Use GCPROTECT_BEGININTERIOR to protect pointers into arrays during array marshalling

[jkoritzinsky]

Fixes #123271
Fixes #123269
Fixes #121690

Failures introduced by #121362 where we changed the string->BSTR array marshalling to call back into managed code. This introduces a transition where the code was not expecting one where GC can trigger.

Update the BSTR marshalling to use GCPROTECT_BEGININTERIOR to ensure that our pointer into the managed array is updated by the GC.

A bunch of this code used various different patterns (manually adjusting offsets after a GC if one occurred, recalculating the offset into the array's data each iteration) instead of using GCPROTECT_BEGININTERIOR. This PR adjusts all of the marshallers where GC could possibly occur (any sort of managed or possibly managed marshalling) to all use GCPROTECT_BEGININTERIOR.

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Pull request overview

This PR fixes GC-related crashes in COM interop array marshalling by properly protecting interior pointers into managed arrays using GCPROTECT_BEGININTERIOR. The failures were introduced by PR #121362 which moved BSTR trailbyte tracking out of the sync block, causing transitions to managed code that could trigger GC during array marshalling.

Changes:

• Replaced manual pointer recalculation logic with GCPROTECT_BEGININTERIOR protection
• Updated 10 array marshalling functions to protect interior pointers during GC-triggering operations
• Removed obsolete "unprotected array" tracking code that manually checked if arrays moved

[jkotas]

My guess is that indexing from protected base would be a tiny bit cheaper than GC protected interior pointer (avoids stacks spills, multiplication is cheap). It does not really matter.