[cDAC] Change pointer data to be compile-time constant

[max-charlamb]

• Updates the pointer data array to be a constexpr. On MSVC, this requires enabling a flag to allow external linkage on a constexpr variable.
• StressLog used a global value which was not a compile-time constant (&g_pStressLog->modules). I updated the contract to reference this field as an offset when the StressLog is available. When it is not available it uses the old pointer (StressLogAnalyzer.cs scenario).

[Copilot]

Pull Request Overview

This PR changes pointer data arrays in the cDAC (Contract Data Access) system from runtime values to compile-time constants by making them constexpr. The key motivation is to enable compile-time evaluation of these data structures, which requires special handling for MSVC compiler compatibility.

Key changes:

• Convert pointer data arrays to constexpr with MSVC-specific compiler flag
• Refactor StressLog module table access to use field offsets instead of global pointers
• Update data contracts to support both legacy and new access patterns

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/coreclr/clrdatadescriptors.cmake	Adds MSVC compiler flag /Zc:externConstexpr to enable external linkage on constexpr variables
src/coreclr/debug/datadescriptor-shared/contractpointerdata.cpp	Changes pointer data array from uintptr_t to constexpr void* array
src/coreclr/debug/datadescriptor-shared/contractdescriptorstub.c	Updates pointer data types from uintptr_t* to void**
src/coreclr/debug/datadescriptor-shared/contract-descriptor.c.in	Updates pointer data types from uintptr_t* to void**
src/coreclr/inc/stresslog.h	Changes cdac_offsets template members from const to constexpr
src/coreclr/vm/datadescriptor/datadescriptor.inc	Removes global StressLogModuleTable pointer, adds Modules field to StressLog type
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/StressLog.cs	Adds optional Modules property to support new field-based access
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StressLog.cs	Implements fallback logic to access module table via StressLog field when global pointer unavailable
src/tools/StressLogAnalyzer/src/Program.cs	Adds Modules field definition for StressLogAnalyzer compatibility
docs/design/datacontracts/StressLog.md	Updates documentation to reflect removal of global StressLogModuleTable and addition of Modules field

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[jkoritzinsky]

Stresslog changes LGTM