[cDAC] Update DebugInfo contract for new format

[max-charlamb]

See context for changes: #120303 (comment)

markdown lint failure is unrelated and fixed in: #121421

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[Copilot]

Pull Request Overview

This pull request introduces version 2 of the DebugInfo contract with a unified header format, while refactoring common code into a helper class. The new version replaces the flag byte approach of version 1 with a fat/slim chunk table for better extensibility.

• Adds DebugInfo_2 implementing a new header format that encodes chunk sizes in nibble format
• Extracts the bounds decoding logic into DebugInfoHelpers.DoBounds() for code reuse between versions
• Updates documentation to describe the version 2 header encoding format
• Removes PatchpointInfo data descriptors and related CDAC infrastructure

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/DebugInfo/DebugInfo_2.cs	Implements version 2 of the DebugInfo contract with unified fat/slim header format for chunk size encoding
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/DebugInfo/DebugInfo_1.cs	Refactored to use shared DebugInfoHelpers.DoBounds() method
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/DebugInfo/DebugInfoHelpers.cs	New helper class containing shared bounds decoding logic with parameterized IL offset bias
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/DebugInfo/DebugInfoFactory.cs	Registers version 2 implementation in the factory
src/coreclr/vm/datadescriptor/datadescriptor.inc	Removes PatchpointInfo type definition from CDAC data descriptors
src/coreclr/inc/patchpointinfo.h	Removes CDAC-related template specialization and friend declarations
docs/design/datacontracts/DebugInfo.md	Documents version 2 header encoding and removes incorrect CodeVersions contract reference from version 1

Comments suppressed due to low confidence (1)

src/coreclr/vm/datadescriptor/datadescriptor.inc:667

• The removal of the PatchpointInfo type will break DebugInfo_1 which still depends on it. The DebugInfo_1.cs implementation (lines 51-55) uses DataType.PatchpointInfo to read patchpoint information when the EXTRA_DEBUG_INFO_PATCHPOINT flag is set. This type definition should not be removed unless DebugInfo_1 is also updated to not rely on it, or Version 1 is being completely removed.

CDAC_TYPE_BEGIN(CodeHeapListNode)
CDAC_TYPE_FIELD(CodeHeapListNode, /*pointer*/, Next, offsetof(HeapList, hpNext))
CDAC_TYPE_FIELD(CodeHeapListNode, /*pointer*/, StartAddress, offsetof(HeapList, startAddress))
CDAC_TYPE_FIELD(CodeHeapListNode, /*pointer*/, EndAddress, offsetof(HeapList, endAddress))
CDAC_TYPE_FIELD(CodeHeapListNode, /*pointer*/, MapBase, offsetof(HeapList, mapBase))
CDAC_TYPE_FIELD(CodeHeapListNode, /*pointer*/, HeaderMap, offsetof(HeapList, pHdrMap))
CDAC_TYPE_END(CodeHeapListNode)

[max-charlamb]

Known unrelated failure in runtime-diagnostics cDAC pipeline: #117785