Intent of on_stateSent_buffers_callbacks_and_returns_true

All 3 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 3 tests
- server/ 3 tests
  - service/ 3 tests
    
    history/ 3 tests
    
    workflow/ 3 tests
    
    update/ 3 tests
    
    TestAttachCallbacks/ 3 tests
    
    go.temporal.io/server/service/history/workflow/update/TestAttachCallbacks/on_stateSent_buffers_callbacks_and_returns_true Introduced here
    
    go.temporal.io/server/service/history/workflow/update/TestAttachCallbacks/on_stateSent_dedup_by_requestID_buffers_only_once Inherited update.go ×1
    
    go.temporal.io/server/service/history/workflow/update/TestAttachCallbacks/on_stateSent_multiple_different_requestIDs Inherited update.go ×1