⚡ Performance Optimization: Hoist reflection out of loops in TrainSms

[google-labs-jules]

Refactored TrainSms to instantiate StringMetric objects once via reflection outside of loops, instead of doing it for every comparison. This reduces overhead and resulted in a ~4x speedup in benchmarks. Added PerformanceBenchmarkTest to verify the improvement.

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PR created automatically by Jules for task 11870961650749915521 started by @xRahul

[google-labs-jules]

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