Port internal TS code to JS

[bartlomieju]

This PR converts our internal runtime code to use pure JS instead of TS. It enables future refactors:

• reducing the size of the compiler snapshot.
• removing deno_typescript crate completely
• op crates

This work has been planned extensively beforehand: See the design doc.

Incremental compile: from 2 min down to 30 seconds

touch cli/js/web/fetch.ts; cargo build

master           2m 06s
master           1m 55s

#6756               54s
#6756               51s

this branch         33s
this branch         31s

Release binary size: 1mb smaller

Due to removing source maps for internal code. (Measured on mac.)

master         48122324
this branch    47326308

Code size: ~2700 fewer lines of code

In particular, removes our compile-time TypeScript compiler. This reduces the number of custom TypeScript compilers from 2 to 1.

 214 files changed, 16804 insertions(+), 19549 deletions(-)

[ry]

Happy to add TSDoc - I agree that gets us 90% of the way there. I'm not going to request that Bartek do that in this PR tho.

[nayeemrmn]

• It turns out code related to web APIs is dependent on the
  Deno.build - mostly for deciding on line endings (eg. URL).

Fixed in #6807 (for URL). I'll end up copy-paste merging it over this PR.

[ry]

LGTM

[towertop]

The markdown cli/js/web/README.md was removed. It worked well for looking up the state of Web API implementation. Doesn't it apply for new js2 version?

[ry]

@towertop Thanks for the notice - I've added it back in #6842