[cDAC] Add stackwalk DAC flags

[rcj1]

Fixes #112366

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[Copilot]

Pull request overview

This PR updates the cDAC legacy IXCLRData stack-walk surface to accept flags for IXCLRDataTask.CreateStackWalk, and threads those flags through to ClrDataStackWalk to influence which frames are surfaced during enumeration.

Changes:

• Change IXCLRDataTask.CreateStackWalk to take a new CLRDataStackWalkFlag enum instead of a raw uint.
• Add CLRDataStackWalkFlag and plumb the flag type through ClrDataTask and ClrDataStackWalk.
• Use the provided flags in ClrDataStackWalk to filter which StackWalkState values are considered “legacy visible”.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/IXCLRData.cs	Updates the COM interface signature and introduces CLRDataStackWalkFlag.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataTask.cs	Propagates the new flag type through the task’s CreateStackWalk implementation (including legacy forwarding).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataStackWalk.cs	Stores the flags and applies them when deciding which frames to surface.

Copilot's findings

Suppressed comments (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataTask.cs:86

• This PR adds new flag-dependent behavior for IXCLRDataTask.CreateStackWalk, but the cDAC test suite does not currently exercise IXCLRDataStackWalk enumeration with non-zero flags (or validate that the filtered frame set stays in sync with the legacy DAC when _legacyImpl is present). Adding at least one unit/integration test covering the flag behavior would help prevent regressions.

    int IXCLRDataTask.CreateStackWalk(CLRDataStackWalkFlag flags, DacComNullableByRef<IXCLRDataStackWalk> stackWalk)
    {
        Contracts.ThreadData threadData = _target.Contracts.Thread.GetThreadData(_address);
        if (threadData.State.HasFlag(Contracts.ThreadState.Unstarted))
            return HResults.E_FAIL;

        IXCLRDataStackWalk? legacyStackWalk = null;
        if (_legacyImpl is not null)
        {
            DacComNullableByRef<IXCLRDataStackWalk> legacyStackWalkOut = new(isNullRef: false);
            int hr = _legacyImpl.CreateStackWalk(flags, legacyStackWalkOut);
            if (hr < 0)
                return hr;
            legacyStackWalk = legacyStackWalkOut.Interface;
        }

        stackWalk.Interface = new ClrDataStackWalk(_address, flags, _target, legacyStackWalk);
        return HResults.S_OK;

• Files reviewed: 3/3 changed files
• Comments generated: 3