Intent of flag_on_+_namespace_RE_follows_the_cap

All 3 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 3 tests
- server/ 3 tests
  - common/ 3 tests
    
    TestCreateHistoryClientRetryPolicy_SystemREGating/ 1 test
    
    go.temporal.io/server/common/TestCreateHistoryClientRetryPolicy_SystemREGating/flag_on_+_namespace_RE_follows_the_cap Introduced here
    
    TestCreateHistoryClientRetryPolicy_ThrottleRetryContext/ 1 test
    
    go.temporal.io/server/common/TestCreateHistoryClientRetryPolicy_ThrottleRetryContext/flag_off_caps_at_2_attempts Inherited flag_off_caps_at_2_attempts
    
    go.temporal.io/server/common/TestCreateHistoryClientRetryPolicy_MixedErrorSequence Inherited TestCreateHistoryClientRetryPolicy_MixedErrorSequence