…ven if not emitted

- Don't print the exact command run by rustbuild unless `--verbose` is set.
  This is almost always unhelpful, since it's just cargo with a lot of
  arguments.
- Don't print "Build completed unsuccessfully" unless --verbose is set.
  You can already tell the build failed by the errors above, and the
  time isn't particularly helpful.
- Don't print the full path to bootstrap. This is useless to everyone,
  even including when working on x.py itself. You can still opt-in to
  this being shown with `--verbose`, since it will throw an exception.

Before:

```
error[E0432]: unresolved import `x`
   --> library/std/src/lib.rs:343:5
    |
343 | use x;
    |     ^ no external crate `x`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `std`

To learn more, run the command again with --verbose.
command did not execute successfully: "/home/joshua/rustc4/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "check" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "8" "--release" "--features" "panic-unwind backtrace" "--manifest-path" "/home/joshua/rustc4/library/test/Cargo.toml" "--message-format" "json-render-diagnostics"
expected success, got: exit status: 101
failed to run: /home/joshua/rustc4/build/bootstrap/debug/bootstrap check
Build completed unsuccessfully in 0:00:13
```

After:

```
error[E0432]: unresolved import `x`
   --> library/std/src/lib.rs:343:5
    |
343 | use x;
    |     ^ no external crate `x`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `std`

To learn more, run the command again with --verbose.
```

This makes it possible to use `switch_int_edge_effects` outside
`rustc_mir::dataflow::impls`.

In E0716, there is a code block that is equivalent to the erroneous
code example. Especially when viewed with `rustc --explain`, it's
not obvious that it is also erroneous, and some users have been
confused when they try to change their code to match the erroneous
equivalent.

curl v0.4.36 -> v0.4.38
curl-sys v0.4.42+curl-7.76.0 -> v0.4.44+curl-7.77.0
fixes cve's https://curl.se/docs/vuln-7.76.0.html

E0716: clarify that equivalent code example is erroneous

In E0716, there is a code block that is equivalent to the erroneous
code example. Especially when viewed with `rustc --explain`, it's
not obvious that it is also erroneous, and some users have been
confused when they try to change their code to match the erroneous
equivalent.

`@rustbot` label +A-diagnostics +D-newcomer-roadblock +T-compiler

…removal, r=Mark-Simulacrum

Add check to ensure error code explanations are not removed anymore even if not emitted

The error explanations are useful in case you use older version of the compiler. Even more if they had an explanation. If they are not emitted, their explanations should be updated but not removed (as we did for a few of them, like E0001).

r? `@Mark-Simulacrum`

…mulacrum

Make x.py less verbose on failures

- Don't print the exact command run by rustbuild unless `--verbose` is set.
  This is almost always unhelpful, since it's just cargo with a lot of
  arguments (and you can't replicate it anyway unless you have the environment variables, which aren't printed by default).
- Don't print "Build completed unsuccessfully" unless --verbose is set.
  You can already tell the build failed by the errors above, and the
  time isn't particularly helpful.
- Don't print the full path to bootstrap. This is useless to everyone,
  even including when working on x.py itself. You can still opt-in to
  this being shown with `--verbose`, since it will throw an exception.

Before:

```
error[E0432]: unresolved import `x`
   --> library/std/src/lib.rs:343:5
    |
343 | use x;
    |     ^ no external crate `x`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `std`

To learn more, run the command again with --verbose.
command did not execute successfully: "/home/joshua/rustc4/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "check" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "8" "--release" "--features" "panic-unwind backtrace" "--manifest-path" "/home/joshua/rustc4/library/test/Cargo.toml" "--message-format" "json-render-diagnostics"
expected success, got: exit status: 101
failed to run: /home/joshua/rustc4/build/bootstrap/debug/bootstrap check
Build completed unsuccessfully in 0:00:13
```

After:

```
error[E0432]: unresolved import `x`
   --> library/std/src/lib.rs:343:5
    |
343 | use x;
    |     ^ no external crate `x`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `std`

To learn more, run the command again with --verbose.
```

cc rust-lang#86854, rust-lang#86022

r? `@Mark-Simulacrum`

…-str, r=Mark-Simulacrum

Stabilize `string_drain_as_str`

Closes rust-lang#76905, FCP is done: rust-lang#76905 (comment)

Add a regression test for issue-69323

Closes rust-lang#69323
r? `@jackh726`

…cts, r=jonas-schievink

re-export SwitchIntEdgeEffects

This makes it possible to use `switch_int_edge_effects` outside
`rustc_mir::dataflow::impls`.

…ed, r=JohnTitor

Add missing code example for Write::write_vectored

Bump deps

tidy: updated cargo_metadata to 0.12 (rustfmt only one left, that depends on 0.8 version in tree, waiting when it merges into rustc repo)

miow v0.3.6 -> v0.3.7, drops socket2 v0.3.19

curl v0.4.36 -> v0.4.38
curl-sys v0.4.42+curl-7.76.0 -> v0.4.44+curl-7.77.0
fixes CVE's https://curl.se/docs/vuln-7.76.0.html