Intent of operation_already_completed, completed_event_deletes_node

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
  - components/ 2 tests
    
    nexusoperations/ 2 tests
    
    workflow/ 2 tests
    
    TestHandleCancelCommand/ 1 test
    
    go.temporal.io/server/components/nexusoperations/workflow/TestHandleCancelCommand/operation_already_completed Introduced here
    
    TestOperationNodeDeletionOnTerminalEvents/ 1 test
    
    go.temporal.io/server/components/nexusoperations/workflow/TestOperationNodeDeletionOnTerminalEvents/completed_event_deletes_node Introduced here