Use concurrent dictionary in NameMultiMap for CE yield cache

[vzarytovskii]

This might fix ionide/ionide-vscode-fsharp#2035, until we have a better stack, this is our best guess what's happening (the only related change between 8.0.300 - 8.0.400).

Full list of changes between: release/dev17.10...release/dev17.11

If anyone has better idea, feel free to chime in.

[github-actions]

❗ Release notes required

@vzarytovskii,

Caution

No release notes found for the changed paths (see table below).

Please make sure to add an entry with an informative description of the change as well as link to this pull request, issue and language suggestion if applicable. Release notes for this repository are based on Keep A Changelog format.

The following format is recommended for this repository:

* <Informative description>. ([PR #XXXXX](https://github.com/dotnet/fsharp/pull/XXXXX))

See examples in the files, listed in the table below or in th full documentation at https://fsharp.github.io/fsharp-compiler-docs/release-notes/About.html.

If you believe that release notes are not necessary for this PR, please add NO_RELEASE_NOTES label to the pull request.

You can open this PR in browser to add release notes: open in github.dev

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.100.md	No release notes found or release notes format is not correct

[vzarytovskii]

/backport to release/dev17.11

[github-actions]

Started backporting to release/dev17.11: https://github.com/dotnet/fsharp/actions/runs/10472290516

[github-actions]

@vzarytovskii backporting to release/dev17.11 failed, the patch most likely resulted in conflicts:

$ git am --3way --ignore-whitespace --keep-non-patch changes.patch

Applying: Use concurrent dictionary in NameMultiMap for CE yield cache
Using index info to reconstruct a base tree...
M	src/Compiler/Checking/CheckDeclarations.fs
M	src/Compiler/Utilities/HashMultiMap.fs
M	src/Compiler/Utilities/HashMultiMap.fsi
Falling back to patching base and 3-way merge...
Auto-merging src/Compiler/Utilities/HashMultiMap.fsi
Auto-merging src/Compiler/Utilities/HashMultiMap.fs
CONFLICT (content): Merge conflict in src/Compiler/Utilities/HashMultiMap.fs
Auto-merging src/Compiler/Checking/CheckDeclarations.fs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 Use concurrent dictionary in NameMultiMap for CE yield cache
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

[github-actions]

@vzarytovskii an error occurred while backporting to release/dev17.11, please check the run log for details!

Error: git am failed, most likely due to a merge conflict.