🧪 [testing improvement] Add unit and concurrency tests for SynchronizedCollection<T>

[johnstrand]

🎯 What: Missing unit tests for abstract class SynchronizedCollection.

📊 Coverage: Added test cases covering Add, Remove, Integrate, Get, ClearPending, WaitForIntegration, snapshot caching/dirty flag handling, generic/non-generic enumerators, and multi-threaded concurrency scenarios.

✨ Result: Improved test coverage and reliability for thread-safe collection operations in GameUtils.Types.Collections.

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PR created automatically by Jules for task 13379090349523441136 started by @johnstrand

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