Intent of nexus_content_with_length_header

All 1 exact test in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 1 test
- server/ 1 test
  - common/ 1 test
    
    nexus/ 1 test
    
    TestNexusPayloadSerializer/ 1 test
    
    go.temporal.io/server/common/nexus/TestNexusPayloadSerializer/nexus_content_with_length_header Introduced here