Intent of mixed_tags_normalize_only_excluded_ones

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
    
    metrics/ 2 tests
    
    TestNormalizeTagsForCaching/ 1 test
    
    go.temporal.io/server/common/metrics/TestNormalizeTagsForCaching/mixed_tags_normalize_only_excluded_ones Introduced here
    
    go.temporal.io/server/common/metrics/TestTallyScope Inherited TestTallyScope