Intent of nil_override_returns_nil

All 1 exact test in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 1 test
- server/ 1 test
  - common/ 1 test
    
    worker_versioning/ 1 test
    
    TestValidateVersioningOverrideAndGetReactivationEligibility/ 1 test
    
    go.temporal.io/server/common/worker_versioning/TestValidateVersioningOverrideAndGetReactivationEligibility/nil_override_returns_nil Introduced here