Intent of valid, round-trip_with_escaped_path

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
    
    nexus/ 2 tests
    
    TestConvertNexusLinkToLinkActivity/ 2 tests
    
    go.temporal.io/server/common/nexus/TestConvertNexusLinkToLinkActivity/round-trip_with_escaped_path Introduced here
    
    go.temporal.io/server/common/nexus/TestConvertNexusLinkToLinkActivity/valid Introduced here