Share ObjectiveCMarshal reference-tracking storage between CoreCLR and NativeAOT

[Copilot]

ObjectiveCMarshal had divergent CoreCLR and NativeAOT implementations for tagged reference-tracking memory. This change moves CoreCLR to the same ConditionalWeakTable<object, ObjcTrackingInformation> model used by NativeAOT and updates diagnostics contracts accordingly.

• Description
  • CoreCLR managed ObjectiveCMarshal now owns tagged memory
    • Added CoreCLR-side s_objects CWT and ObjcTrackingInformation lifecycle logic in ObjectiveCMarshal.CoreCLR.cs.
    • Unified CreateReferenceTrackingHandle / GetOrCreateReferenceTrackingMemory flow to use managed CWT-backed memory for both runtimes.
    • Initialize now passes the CWT instance to native for unmanaged lookup during GC callbacks.
  • CoreCLR native Objective-C interop path no longer uses syncblk tagged storage
    • Removed Objective-C-specific syncblk tagged-memory allocation/retrieval path from interoplibinterface_objc.cpp.
    • Replaced with unmanaged CWT lookup (ConditionalWeakTableObject::TryGetValue) to resolve tagged memory from managed state.
    • Split QCall responsibilities so native only allocates the ref-counted handle (ObjCMarshal_AllocateReferenceTrackingHandle).
  • Unmanaged CWT accessor usage enabled in runtime path
    • Exposed ConditionalWeakTable native lookup helpers for this suspended-runtime callback scenario and clarified constraints in comments.
  • cDAC ObjectiveCMarshal contract moved to shared model
    • Added ObjectiveCMarshal contract c2 that reads tagged memory via ObjectiveCMarshal.s_objects and CWT entries.
    • Registered c2 in CoreCLR contract registry and updated descriptor contract version.
    • Added new data mappings for ObjectiveCMarshal static table and ObjcTrackingInformation._memory.

// CoreCLR native callback path now resolves tagged memory from managed CWT state.
CONDITIONAL_WEAK_TABLE_REF trackingTable = (CONDITIONAL_WEAK_TABLE_REF)ObjectFromHandle(g_ObjectiveCTrackingInfoTable);
OBJECTREF trackingInfoObj = NULL;
if (!trackingTable->TryGetValue(object, &trackingInfoObj))
    return false;

OBJC_TRACKING_INFO_REF trackingInfo = (OBJC_TRACKING_INFO_REF)trackingInfoObj;
void* taggedLocal = (void*)trackingInfo->_memory;

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[rcj1]

We aren’t revving the versions yet.

[AaronRobinsonMSFT]

My assumption here is the current cDAC works on .NET 10 for Objective-C. This is a break change so I assume we need to ensure .NET 10 continues to work.

[rcj1]

We do not support .NET 10 with cDAC. We are making changes to the runtime throughout .NET 11 to support cDAC, for example #125243.

[rcj1]

Any individual API or contract may just happen to work, but that is not a guarantee or promise.