perf: avoid creating closure

[TimothyMakkison]

Prevent closure creation for AssmeblyMetada and ClassMetadata, using GetOrAdd<TArg>(TKey, Func<TKey,TArg,TValue>, TArg)

• Also removed an extra line

Not a massive saving probably around 100KB on TUnit.TestProject

[thomhurst]

Summary

Eliminates closure allocations in metadata caching hot paths by using the state-passing overload of ConcurrentDictionary.GetOrAdd.

Critical Issues

None found ✅

Suggestions

None - this is a clean performance optimization that aligns perfectly with TUnit's "Performance First" principle. The use of static lambdas with the state-passing GetOrAdd overload is exactly the right approach for hot path allocation reduction.

Verdict

✅ APPROVE - No critical issues

Great optimization! This is precisely the kind of hot path improvement that benefits test discovery performance across all TUnit projects.