[cDAC] Implement GetThreadOwningMonitorLock for cDAC

[barosiak]

Summary

Implement GetThreadOwningMonitorLock in DacDbiImpl.

Changes

• DacDbiImpl.cs - Implement GetThreadOwningMonitorLock with #if DEBUG legacy validation.
• DacDbiImplTests.cs - Add 8 tests for lock-not-held and lock-held scenarios.

[dotnet-policy-service]

Tagging subscribers to this area: @steveisok, @tommcdon, @dotnet/dotnet-diag
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR implements the IDacDbiInterface.GetThreadOwningMonitorLock path in the managed cDAC (DacDbiImpl) and adds xUnit coverage for “lock held” vs “lock not held” scenarios using mocked IObject/ISyncBlock/IThread contracts.

Changes:

• Implement GetThreadOwningMonitorLock by reading sync-block lock info, then resolving the owning Thread by ThreadData.Id, with #if DEBUG parity validation against the legacy DAC implementation.
• Add a new [Theory] to validate returned DacDbiMonitorLockInfo.lockOwner and acquisitionCount for held/unheld cases across standard mock architectures.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs	Adds the cDAC implementation of GetThreadOwningMonitorLock with legacy parity validation under #if DEBUG.
src/native/managed/cdac/tests/DacDbiImplTests.cs	Adds xUnit coverage for lock-held vs lock-not-held behavior across architectures using mocked contracts.

[noahfalk]

LGTM assuming we fix that pre-existing DAC bug.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[lateralusX]

LGTM!

[barosiak]

/ba-g unrelated failures, timeouts