AsyncLocal diagnostics, clean slate

[majocha]

We used node CE, a customized async CE variant to ensure DiagnosticsThreadStatics flow from thread to thread along with the execution of asynchronous compiler tasks.

AsyncLocal<'T> achieves this without the need for a specialized CE.

from documetation:

AsyncLocal<T> Class
Represents ambient data that is local to a given asynchronous control flow, such as an asynchronous method.

This allows us to just remove NodeCode and replace node expressions with async.

Tests show AsyncLocal works as expected in scenarios involving task, async, Async.SwitchToNewThread()SwitchToThreadPool(), Thread.Start() as well as TPL parallel execution.

• Added concurrent diagnostics logging for running many computations:

• MultipleDiagnosticsLoggers.Parallel generally for use in place of NodeCode.Parallel. Replays diagnostics onto caller's logger preserving the given order of computations.
• MultipleDiagnosticsLoggers.Sequential replaces NodeCode.Parallel. Unlike Async.Sequential it starts immediately on the same thread so It automatically uses caller's diagnostics context.

• Added tests for AsyncLocal diagnostics flow in async and sync contexts.

Previous attempts: #16602, #16645

[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/8.0.400.md
vsintegration/src	docs/release-notes/.VisualStudio/17.11.md

[majocha]

I think this is good for a review now.

[psfinaki]

Okay so I finally gathered some mental resources for reviewing this :)

I added a few remarks and questions mostly for my understanding. Overall these are good changes since removing custom CEs reduces cognitive load of the code. Also I think it's a good moment to get this in.

Thanks!

[vzarytovskii]

@majocha i saw reports from @ForNeVeR that some of the changes result in the deadlock

[majocha]

ah, ok I'm seeing the issue now.