Intent of TestExtractMetadataFromTrailer_PrefersProtoKey, TestExtractMetadataFromTrailer_ControlCharsInProto

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
    
    rpc/ 2 tests
    
    interceptor/ 2 tests
    
    go.temporal.io/server/common/rpc/interceptor/TestExtractMetadataFromTrailer_ControlCharsInProto Introduced here
    
    go.temporal.io/server/common/rpc/interceptor/TestExtractMetadataFromTrailer_PrefersProtoKey Introduced here