Intent of sets_event_attributes_with_UserMetadata_and_spawns_a_child_operation_machine

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
  - components/ 1 test
    
    nexusoperations/ 1 test
    
    workflow/ 1 test
    
    TestHandleScheduleCommand/ 1 test
    
    go.temporal.io/server/components/nexusoperations/workflow/TestHandleScheduleCommand/sets_event_attributes_with_UserMetadata_and_spawns_a_child_operation_machine Introduced here