Scoped nowarn

[Martin521]

Description

Implements Scoped Nowarn according to draft RFC FS-1146.

This PR has taken a while. I had to deal with much more complexity than I imagined when I naively volunteered to tackle the feature request. Anyway, here we are.

I have split the PR into 7 commits that can be reviewed in sequence.
All of them compile, 1 and 4 - 7 also pass all tests locally.

1. Add the feature flag, baseline tests, and the core WarnScopes module. See src/Compiler/SyntaxTree/WarnScopes.fsi and the RFC for the functionality of the module.

2. Add the necessary changes to lexing and parsing. Note that the warn directives can no longer be collected during parsing (since they can now appear not only in top-level modules, but anywhere). So we collect them during lexing, similar to the processing of #if/#else/#endif directives.

3. Remove legacy #nowarn processing (but hold off AST changes)

4. Integrate the WarnScopes functionality and test it

5. Add warn directive trivia (but hold off AST changes)

6. Enable warn directive trivia (which means AST changes)

7. Remove defunct types and parameters related to former #nowarn processing (more AST changes)

There is also a separate commit for the IlVerify baseline updates (change in line numbers only)

Checklist

• Test cases added
• Performance benchmarks added in case of performance changes
• Release notes entry updated
• Create documentation update PRs (see RFC)

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.300.md
LanguageFeatures.fsi	docs/release-notes/.Language/preview.md

[psfinaki]

Hi @Martin521 - thanks for the contribution. It's a substantial effort and we appreciate it. The PR is on our radar - just keep in mind that it's big and specific, and it will take time to find capacity for it.

If anyone from the community gets to thoroughly review it, that would be valuable as well.

Thanks for your diligence and patience :)

[auduchinok]

Any reason to make it internal?

We should somehow make the scopes information accessible to FCS users, given that the previous implementation is removed from SyntaxTree.

[Martin521]

The directives are available as trivia (now in ParsedImplFileInputTrivia / ParsedSigFileInputTrivia), see commit 5 of this PR.
But if more information is useful for tooling, please let me know what I should make available.

[auduchinok]

Helpers like IsWarnon and IsNowarn are definitely useful.

[Martin521]

I made IsWarnon and IsNowarn public.
I would recommend, though, to rather rely on the filtering mechanism of the diagnostics loggers of the compiler (which use these two functions internally).