[cDAC] Follow-up items from PR #126713 (typed field extension methods)

[max-charlamb]

Follow-up items from #126713

This issue tracks outstanding items identified in the review comments on #126713 ([cDAC] Add typed field extension methods for Data classes).

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1. Typed field extension methods for globals

Requested by @rcj1 in this comment: extend the new typed field helpers to cover globals (currently only per-object fields are covered).

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2. Incomplete conversion — several Data classes still use old target.Read pattern

The following files were not converted to the new ReadField/ReadPointerField extension methods:

• Debugger.cs
• CardTableInfo.cs
• CodeHeap.cs
• HostCodeHeap.cs
• RegionFreeList.cs
• AuxiliarySymbolInfo.cs
• InteropSyncBlockInfo.cs
• NativeCodeVersionNode.cs — OptimizationTier (line 24) still uses target.Read<uint>(address + ...)
• GCHeapSVR.cs — FreeableSohSegment / FreeableUohSegment use ContainsKey + ReadPointer instead of ReadPointerFieldOrNull

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cc @max-charlamb @rcj1

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