⚡ Optimize GetComponent usage in GPUInstancerRuntimeData

[marko1olo]

💡 What:
Replaced allocating GetComponent<MeshFilter>() calls with non-allocating TryGetComponent<MeshFilter>(out MeshFilter meshFilter) in multiple tight loops within GPUInstancerRuntimeData.cs. Where possible, the resulting component is cached and reused (such as in AddRenderer) to avoid repeated dictionary lookups.

🎯 Why:
Calling GetComponent creates GC allocations when components are missing, and invokes expensive C++/C# transition boundary overhead. Replacing this with TryGetComponent and hoisting/caching the results natively removes a significant source of stutter in large loops processing mesh renderers.

📊 Measured Improvement:
Due to test framework limitations in this environment context (libhostpolicy.so missing for standalone C# benchmark builds, and exclusion of editor tests in the terminal dotnet test runner), I could not execute a terminal benchmark. However, Unity profiling historically shows that GetComponent<T>() causes noticeable performance penalties due to GC allocations (when missing) and native-boundary transitions when compared to C# 7 TryGetComponent cached usages, especially when iterating over thousands of GameObjects in rendering pathways.

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PR created automatically by Jules for task 12848943296384888927 started by @marko1olo

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