cDAC: extend GCREFS stress coverage to non-Windows / ARM targets

[max-charlamb]

Summary

After PR #129858, GcScanner.PromoteCallerStack synthesizes a GCRefMap blob via ICallingConvention.TryComputeArgGCRefMapBlob and walks every transition Frame's caller-stack refs end-to-end. The GCREFS cdacstress suite is enforced to have zero KnownIssues on Windows x86 / x64 (CdacStressTestBase.AssertAllPassed).

On all other targets the assertion is relaxed to "no hard failures" because TryComputeArgGCRefMapBlob either is not implemented for the platform's calling convention or has known gaps. This tracking issue covers extending coverage so the strict assertion can be enabled everywhere.

Targets that need work

Target	Gap
Linux x64 / macOS x64 (SystemV-AMD64)	Struct-in-register classification per the SystemV ABI is not implemented in CallingConvention_1.ComputeArgGCRefMapBlobCore.
Linux ARM64 / macOS ARM64 (AAPCS64)	Struct-in-register classification per the AAPCS64 / Apple ARM64 variant is not implemented.
Windows ARM64	ARM64 ArgIterator + GCRefMap encoding port not done.
Linux ARM32	ARM32 ABI port (ArgIterator + GCRefMap) not done.

Definition of done

For each target above:

1. ICallingConvention.TryComputeArgGCRefMapBlob produces a byte-identical blob to the runtime's GcInfoEncoder output (verified by the [ARGITER] sub-check in cdacstress).
2. CdacStressTestBase.AssertAllPassed is broadened to require KnownIssues == 0 on the target.
3. The WindowsOnly / Windows-x86-or-x64 gate is removed from the corresponding test in CdacStressTests.cs.

Related

• PR [cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0 known issues on windows-x86/x64 #129858 -- enables strict KnownIssues == 0 on Windows x86 / x64.
• cDAC: GCInfo decoder does not support x86 #126359 -- x86 GCInfo decoder (resolved by [cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0 known issues on windows-x86/x64 #129858).
• Portable Data Contract-based DAC #99298 -- Portable Data Contract-based DAC (umbrella).

Note

This issue was authored with assistance from GitHub Copilot.

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