Implement ISOSDacInterface::GetObjectClassName in cDAC SOSDacImpl

[Copilot]

Description

Implements the cDAC version of ISOSDacInterface::GetObjectClassName in SOSDacImpl.cs, replacing the legacy-only stub. Based on ClrDataAccess::GetObjectClassName in request.cpp, following the established pattern from GetMethodTableName.

Implementation (SOSDacImpl.cs)

• Gets the object's MethodTable via IObject.GetMethodTableAddress, then resolves the TypeHandle via IRuntimeTypeSystem.GetTypeHandle
• Handles unloaded modules ("<Unloaded Type>") and normal types via TypeNameBuilder.AppendType with FormatNamespace | FormatFullInst
• Falls back to DacStreams.StringFromEEAddress when TypeNameBuilder throws
• Includes #if DEBUG validation against legacy DAC

Unit tests (ObjectTests.cs)

• GetObjectClassName_ZeroAddress — zero address returns error HResult
• GetObjectClassName_UnloadedModule — object with unloaded module returns "<Unloaded Type>" (uses Moq to mock IObject, IRuntimeTypeSystem, and ILoader contracts)
• GetObjectClassName_NullBufferReturnsNeededSize — null buffer still populates needed size

All 3 tests run across 4 architectures (32/64-bit × little/big-endian).

Dump tests (RuntimeTypeSystemDumpTests.cs)

• RuntimeTypeSystem_ObjectMethodTableHasLoadedModule — verifies System.Object MT → module → loaded image flow
• RuntimeTypeSystem_StringMethodTableHasLoadedModule — same for System.String

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[max-charlamb]

@copilot , address feedback

[Copilot]

@copilot , address feedback

All feedback addressed in 0239f9f.

[Copilot]

Pull request overview

Implements the cDAC version of ISOSDacInterface::GetObjectClassName in SOSDacImpl, replacing the legacy-only stub, and adds unit + dump-based tests to validate method-table → type/module resolution and string output behavior.

Changes:

• Add cDAC implementation of GetObjectClassName using IObject, IRuntimeTypeSystem, ILoader, and TypeNameBuilder with a fallback to DacStreams.
• Add unit tests covering zero address, unloaded-type naming, and “null buffer returns needed size” behavior.
• Add dump-based integration tests validating that System.Object and System.String resolve to modules with loaded image contents.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Implements GetObjectClassName in cDAC, including unloaded-module handling, TypeNameBuilder formatting, and DEBUG cross-check vs legacy DAC.
src/native/managed/cdac/tests/ObjectTests.cs	Adds unit tests for GetObjectClassName argument handling and unloaded-type naming behavior.
src/native/managed/cdac/tests/DumpTests/RuntimeTypeSystemDumpTests.cs	Adds dump tests ensuring Object/String MTs map to modules with loaded image contents via Loader contract.