perf: skip List creation in GetDynamicTestAttributes

[TimothyMakkison]

Skip List creation if TestClassType is null.

• Would be a good candidate for ValueListBuilder if this is a hot path

[thomhurst]

APPROVE - Clean performance optimization. Avoids List allocation when TestClassType is null and removes redundant .OfType conversions. Both AotTestDataCollector and ReflectionTestDataCollector updated identically (dual-mode Rule #1). Reduces allocations in test discovery hot path (Rule #4 Performance First). No critical issues found.