[release/8.0] Add boolean field to indicate whether or not the Windows thread pool is being used

[github-actions]

Backport of #90551 to release/8.0

/cc @eduardo-vp

Customer Impact

This field will be used by the !threadpool SOS command to allow customers debug applications using the Windows thread pool.

Testing

The runtime correctly builds with no issues.

Risk

Very low.

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

[ghost]

Tagging subscribers to this area: @mangod9
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Backport of #90551 to release/8.0

/cc @eduardo-vp

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Threading
Milestone:	-

[kouvel]

Thanks!

[jeffschwMSFT]

@eduardo-vp is there a corresponding sos change coming to read this value?

[eduardo-vp]

Yes, there's this one for the diagnostics repo dotnet/diagnostics#4160 and this one for the clrmd repo microsoft/clrmd#1175. I already tested the !threadpool command with both changes and it's working correctly. However both depend on this field being present in the runtime.

[jeffschwMSFT]

approved. we can merge when ready

[carlossanlop]

Failures are:
#90605
#90834
#90639