Implement ISOSDacInterface::GetRegisterName in cDAC SOSDacImpl

[Copilot]

Description

Implements GetRegisterName in SOSDacImpl.cs using the RuntimeInfo contract instead of delegating to the legacy DAC. This mirrors the logic in ClrDataAccess::GetRegisterName (request.cpp) but uses IRuntimeInfo.GetTargetArchitecture() at runtime to select register names, rather than compile-time #ifdef guards.

Implementation (SOSDacImpl.cs)

• Register name arrays for X64, X86, ARM, ARM64, LoongArch64, RiscV64 matching the C++ source
• Caller frame encoding: negative regNum → "caller.<reg>" via -(reg+1), using a separate regIndex local to avoid mutating the parameter
• NullReferenceException thrown inside the try block when both buffer and pNeeded are null (HResult maps to E_POINTER), following the established pattern in the file (e.g., IsRCWDCOMProxy)
• E_UNEXPECTED for out-of-range register index
• S_FALSE when buffer is too small (partial copy via OutputBufferHelpers)
• #if DEBUG legacy DAC comparison using the unmutated regName parameter directly

Tests (GetRegisterNameTests.cs)

• 32 tests covering all 6 architectures, caller frame prefix, null/small buffer handling, out-of-range indices, and unsupported architecture (Wasm)

Fixes #124823

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[max-charlamb]

@copilot, fix the failing CI run and address feedback

[Copilot]

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[Copilot]

Pull request overview

This PR implements the GetRegisterName method in the cDAC SOSDacImpl class, replacing the legacy DAC delegation with a contract-based implementation. The implementation uses the RuntimeInfo contract to dynamically determine the target architecture at runtime, eliminating the need for compile-time #ifdef guards used in the C++ version.

Changes:

• Implements GetRegisterName using IRuntimeInfo.GetTargetArchitecture() to select architecture-specific register name arrays
• Adds register name arrays for all six supported architectures (X64, X86, ARM, ARM64, LoongArch64, RiscV64)
• Includes comprehensive test coverage with 32 tests across all architectures and edge cases

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Implements GetRegisterName with architecture-specific register arrays, caller frame encoding, error handling, and DEBUG legacy comparison
src/native/managed/cdac/tests/GetRegisterNameTests.cs	Adds comprehensive tests covering all architectures, caller frames, null/small buffers, out-of-range indices, and unsupported architecture scenarios

[max-charlamb]

lgtm

[rcj1]

Lgtm