TASK-209191 block global trace while inheriting thread data

[balupillai]

Note

Medium Risk
Touches GC/thread synchronization by adding collector blocking around luaC_inherit_thread, which could introduce or resolve subtle deadlock/timing issues in a highly concurrent, correctness-critical path.

Overview
Prevents global tracing/collector activity from interleaving with thread reclamation by blocking the collector during luaC_inherit_thread while it steals objects, updates ownership, and removes the reclaimed heap from all_heaps.

This adds per-thread state retrieval and a block_collector/unblock_collector bracket around the critical section to reduce lock contention/races between global trace and thread inheritance.

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[Copilot]

Pull request overview

This PR aims to prevent the global tracing GC from running while a thread’s heap/object data is being inherited into another thread, by adding an explicit collector barrier around the inheritance operation.

Changes:

• Add per-OS-thread state lookup in luaC_inherit_thread.
• Block the collector before inheriting a thread’s heap contents and unblock afterward.

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