Use SHash as DAC instance hash

[hoyosjs]

Replaces the hand-rolled hash table implementation in DacInstanceManager withan SHash based implementation. This hash is more efficient for the high volume of find operations the DAC issues when verifying cached cross-process reads. During mini dump collection, DacInstanceManager is the central cache for all memory read from the target process. The hand-rolled hash table used a fixed bucket array that degraded quickly for Find and insertion operations.

Measured minidump collection against a repro app with 2.5k frame deep stacks over 50 threads and the speedup was roughly 9.5x.

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[Copilot]

Pull request overview

This PR replaces the std::unordered_map-based hash table in DacInstanceManager with an SHash-based implementation by removing the #define DAC_HASHTABLE that previously selected the hand-rolled hash table, activating the #else branch which now uses SHash instead of std::unordered_map. This yields a ~9.5x speedup for minidump collection on deep-stack scenarios.

Changes:

• Remove #define DAC_HASHTABLE and the std::unordered_map / std::hash_compare based implementation, replacing it with SHash<DacInstanceSHashTraits>
• Update all hash table operations (Add, Find, Supersede, Flush, ClearEnumMemMarker, DumpAllInstances) to use SHash APIs (LookupPtr, ReplacePtr, Remove, RemoveAll, Begin/End)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/debug/daccess/dacimpl.h	Replace std::unordered_map types with SHash<DacInstanceSHashTraits> and custom traits class
src/coreclr/debug/daccess/daccess.cpp	Update all hash operations to SHash API calls

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[hoyosjs]

/ba-g iOS failures are deadletters.