This adds `WasiHttpHandler`, a new implementation of `HttpMessageHandler` based
on
[wasi:http/outgoing-handler](https://github.com/WebAssembly/wasi-http/blob/v0.2.0/wit/handler.wit),
plus tweaks to `System.Threading` to allow async `Task`s to work in a
single-threaded context, with `ThreadPool` work items dispatched from an
application-provided event loop.

WASIp2 supports asynchronous I/O and timers via `wasi:io/poll/pollable` resource
handles.  One or more of those handles may be passed to `wasi:io/poll/poll`,
which will block until at least one of them is ready.  In order to make this
model play nice with C#'s `async`/`await` and `Task` features, we need to
reconcile several constraints:

- WASI is currently single-threaded, and will continue to be that way for a while.
- C#'s `async`/`await` and `Task` features require a working `ThreadPool` implementation capable of deferring work.
- A WASI component can export an arbitrary number of functions to the host, and though they will always be called synchronously from the host, they need to be able to perform asynchronous operations before returning.
- WASIp3 (currently in the design and prototype phase) will support asynchronous exports, with the top level event loop running in the host instead of the guest, and `wasi:io/poll/pollable` will no longer exist.  Therefore, we don't want to add any temporary public APIs to the .NET runtime which will become obsolete when WASIp3 arrives.

The solution we arrived at looks something like this:

- Tweak the existing `ThreadPool` implementation for WASI so that methods such as `RequestWorkerThread` don't throw `PlatformNotSupportedException`s (i.e. allow work items to be queued even though the "worker thread" is always the same one that is queuing the work)
- Add two new methods to `Thread`:
    - `internal static void Dispatch`: Runs an iteration of event loop, draining the `ThreadPool` queue of ready work items and calling `wasi:io/poll/poll` with any accumulated `pollable` handles
    - `internal static Task Register(int pollableHandle)`: Registers the specified `pollable` handle to be `poll`ed during the next call to `Dispatch`
    - Note that these methods are `internal` because they're temporary and should not be part of the public API, but they are intended to be called via `UnsafeAccessor` by application code (or more precisely, code generated by `wit-bindgen` for the application)

The upshot is that application code can use `wit-bindgen` (either directly or
via the new `componentize-dotnet` package) to generate async export bindings
which will provide an event loop backed by `Thread.Dispatch`.  Additionally,
`wit-bindgen` can transparently convert any `pollable` handles returned by WASI
imports into `Task`s via `Thread.Register`, allowing the component to `await`
them, pass them to a combinator such as `Task.WhenEach`, etc.

Later, when WASIp3 arrives and we update the .NET runtime to target it, we'll be
able to remove some of this code (and the corresponding code in `wit-bindgen`)
without requiring significant changes to the application developer's experience.

This PR contains a few C# source files that were generated by `wit-bindgen` from
the official WASI WIT files, plus scripts to regenerate them if desired.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

switch to `wasm32-wasip2` and update WASI test infra

Now that we're using WASI-SDK 22, we can target `wasm32-wasip2`, which produces
components by default and includes full `wasi:sockets` support.  In order to run
those components, I've updated the test infrastructure to use Wasmtime 21 (the
latest release as of this writing).

Other changes of note:

- Tweaked src/coreclr/jit/compiler.cpp to make `Debug` builds work on Linux

- Added libWasiHttp.a, which includes the encoded component type (in the form of a pre-generated Wasm object file) and a `cabi_realloc` definition.  Both of these are generated by `wit-bindgen` and required by `wasm-component-ld` to generate a valid component.

- Added a `FindWasmHostExecutableAndRun.sh` script for running the WASI tests on UNIX-style platforms.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

various WASI build tweaks

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

quote libWasiHttp.a path in custom linker arg

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

fix wasm-component-ld download command

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

tweak EmccExtraArgs in CustomMain.csproj so wasm-component-ld understands it

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

update CMake minimum version in wasi-sdk-p2.cmake

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

use `HeaderDescriptor` to sort content and response headers

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

allow building native WASI test code in src/tests/build.sh

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

allow WASI runtime tests to be built and run on non-Windows systems

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

update runtime tests to work with WASIp2

As of this writing, WASIp2 [does not support process exit
statuses](WebAssembly/wasi-cli#11) beyond 0 (success)
and 1 (failure).  To work around this, I've modified the relevant tests to
return 0 on success instead of 100.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

fix CI for Windows builds; remove unused file

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

disable sprintf warning in llvmlssa.cpp on macOS

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

remove LibraryWorld_cabi_realloc.o

I didn't mean to add this to Git.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

rename `generate-bindings.sh` files for clarity

This makes it more obvious that, though they are similar, they each have a
different job.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

update to `wit-bindgen` 0.27.0 and regenerate bindings

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

reorganize code; add HttpClient smoke test

- move System/WASIp2 to System/Threading/WASIp2
- remove generated `cabi_realloc` functions since `wasi-libc` will provide one
- add HttpClient test to SmokeTests/SharedLibrary

Note that I put the HttpClient test in SmokeTests/SharedLibrary since we were
already using NodeJS for that test, and adding a simple loopback webserver to
SharedLibraryDriver.mjs was easiest option available to keep the whole test
self-contained.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

implement SystemNative_SysLog for WASI

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

increase NodeJS stack trace limit to 200

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

give guest no filesystem access in SharedLibraryDriver.mjs

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

switch to Trace.Assert into HttpClient smoke test

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

rename WASIp2 directory to Wasi

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

fix non-GET methods and add HttpClient echo test

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

use azure NPM

rename

- WasiEventLoop.RegisterWasiPollable
- WasiEventLoop.DispatchWasiEventLoop

to make it less confusing on the Thread class

- unification of gen-buildsys

- cleanup pal_process_wasi.c

fix build?

more

buffer /echo request body in SharedLibraryDriver.mjs

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

fix gen-buildsys.sh regression

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

allow only infinite `HttpClient.Timeout`s on WASI

This temporary code will be reverted once we support `System.Threading.Timer` on
WASI in a forthcoming PR.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

use `&` operator to simplify install-jco.ps1

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

remove redundant `CheckWasmSdks` target from SharedLibrary.csproj

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

split `FindWasmHostExecutable.sh` out of `FindWasmHostExecutableAndRun.sh`

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

replace component type object files with WIT files

This updates `wit-bindgen` and `wasm-component-ld`, which now support producing
and consuming component type WIT files as an alternative to binary object files.
These files are easier to audit from a security perspective.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

preserve slashes in path in SharedLibrary.csproj

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

temporarily disable ThreadPoolWorkQueue.Dispatch assertion

See dotnet/runtime#104803

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

update `wit-bindgen` to version 0.28.0

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

upgrade to wasi-sdk 24 and wit-bindgen 0.29.0

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

check for WASI in `PhysicalFileProvider.CreateFileWatcher`

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

switch back to WASI 0.2.0

0.2.1 is not yet widely supported, and causes
[trouble](bytecodealliance/jco#486) for Jco, which
rely on for the `SharedLibrary` test.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

remove use of `WeakReference` from `WasiEventLoop`

This was causing `HttpClient` timeout tests in the `SharedLibrary` smoke test
suite to fail, apparently due to `TimerQueue.SetNextTimer` calling
`WasiEventLoop.RegisterWasiPollable`, attaching a continuation to the resulting
`Task` and then letting go of the reference, allowing it to be GC'd.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

skip unsupported signal handling on WASI

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

throw PlatformNotSupportedException in ManualResetEventSlim.Wait on WASI

Otherwise, we end up in an infinite loop.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Revert "switch back to WASI 0.2.0"

This reverts commit a8608b4.

enable `NameResolution` and `Sockets` on WASI

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

set `SocketsHttpHandler.IsEnabled` to `false` on WASI

...at least until we get `System.Net.Sockets` working.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

This requires passing the `CancellationToken` to `WasiEventLoop` and checking it
before polling.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Sometimes there are two Wasm files in Jco's output; sometimes three.  In any
case, hard-coding the number won't fly.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

See bytecodealliance/wit-bindgen#1040

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Otherwise, we end up overwriting `response.Content.Headers`.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

If one or more tasks have been canceled during the call to
`ThreadPoolWorkQueue.Dispatch`, one or more tasks of interest to the application
may have completed, so we return control immediately without polling, allowing
the app to exit if it chooses.

A practical example of this is in the SharedLibrary smoke test.  Without this
patch, that test will take over 100 seconds to complete, whereas with this patch
it completes in under a second.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

...and hopefully make CI happier.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

I'm still investigating whether this actually _is_ a `wasmtime-wasi-http` bug;
stay tuned.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Signed-off-by: Joel Dice <joel.dice@fermyon.com>