[cDAC] Implement IsThreadSuspendedOrHijacked for cDAC

[barosiak]

Summary

Implement IsThreadSuspendedOrHijacked for cDAC.

Changes

• DacDbiImpl.cs - Implement IsThreadSuspendedOrHijacked.
• DacDbiThreadDumpTests.cs - Add a test cross-validating the result against the thread contract.

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[Copilot]

Pull request overview

Implements DacDbiImpl.IsThreadSuspendedOrHijacked in the cDAC legacy DBI shim by deriving the result from the Thread contract’s ThreadData.State, and adds a dump-based integration test that cross-validates the DBI result against the contract’s state flags.

Changes:

• Implement DacDbiImpl.IsThreadSuspendedOrHijacked using IThread.GetThreadData(...).State (DebugSyncSuspended | Hijacked).
• Add a dump test that iterates threads from ThreadStoreData.FirstThread and asserts DBI == contract for suspended/hijacked.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs	Adds the contract-based implementation of IsThreadSuspendedOrHijacked (with DEBUG cross-check against legacy DAC when present).
src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiThreadDumpTests.cs	Adds a dump integration test to validate IsThreadSuspendedOrHijacked results against the Thread contract state.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1

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[Copilot]

Pull request overview

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

Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs:4185

• Avoid using an intentionally-thrown NullReferenceException for the null-output case. This is the only instance in this file that uses exceptions for E_POINTER, and it also makes the GetThreadData call less consistent with nearby thread helpers that explicitly wrap vmThread in a TargetPointer. Prefer setting hr directly when pResult is null, and use new TargetPointer(vmThread) for the contract call.

        {
            if (pResult is null)
                throw new NullReferenceException();

            *pResult = Interop.BOOL.FALSE;