Intent of host_limit_emitted_when_global_limit_is_not_set

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
  - service/ 2 tests
    
    frontend/ 2 tests
    
    TestNamespaceRateLimitMetrics/ 2 tests
    
    go.temporal.io/server/service/frontend/TestNamespaceRateLimitMetrics/host_limit_emitted_when_frontend_service_count_is_not_set Inherited host_limit_emitted_when_frontend_service_count_is_not_set
    
    go.temporal.io/server/service/frontend/TestNamespaceRateLimitMetrics/host_limit_emitted_when_global_limit_is_not_set Introduced here