Integrating GetFrameType and SetContext into cDAC

[Copilot]

• Implement IXCLRStackWalk GetFrameType and SetContext in cDAC
• The CLRDATA_STACK_WALK_REQUEST_SET_FIRST_FRAME Request is a no-op in the context in which we call it - I have left it not implemented.

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[Copilot]

Copilot's findings

Comments suppressed due to low confidence (2)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataStackWalk.cs:67

• Reseed disposes the current enumerator before creating the replacement. If CreateStackWalk/GetEnumerator throws (e.g., invalid context buffer), the stack walk is left with a disposed _dataFrames enumerator, so subsequent calls can start failing even though SetContext returned an HRESULT. Construct the new enumerator first, then swap and dispose the old one after success (transactional update).

    private void Reseed(byte[] context, bool isFirst)
    {
        _dataFrames.Dispose();
        _dataFrames = _target.Contracts.StackWalk.CreateStackWalk(_threadData, context, isFirst).GetEnumerator();
        _currentFrameIsValid = MoveNextLegacyVisible();
    }

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataStackWalk.cs:306

• SetContext always forwards to _legacyImpl.SetContext even when the cDAC SetContext path fails (e.g., invalid context buffer). That can desynchronize the legacy stack walk from the cDAC walk for subsequent GetFrame()/Next() calls (and can mutate legacy state even though SetContext returned failure). Only update the legacy stack walk when this method returns S_OK.

        if (_legacyImpl is not null)
        {
            int hrLocal = _legacyImpl.SetContext(contextSize, context);
#if DEBUG
            Debug.ValidateHResult(hr, hrLocal);

• Files reviewed: 5/5 changed files
• Comments generated: 1

[rcj1]

Fixes #112275