Intent of cluster_not_in_list_is_rejected, empty_current-cluster_name_never_matches

All 2 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 2 tests
- server/ 2 tests
  - common/ 2 tests
    
    namespace/ 2 tests
    
    nsreplication/ 2 tests
    
    TestDefaultAdmitter_Admit/ 2 tests
    
    go.temporal.io/server/common/namespace/nsreplication/TestDefaultAdmitter_Admit/cluster_not_in_list_is_rejected Introduced here
    
    go.temporal.io/server/common/namespace/nsreplication/TestDefaultAdmitter_Admit/empty_current-cluster_name_never_matches Introduced here