R1:21dd79b35af2

When creating or editing a card on a sorted/grouped workboard, adjust headers appropriately

Summary:
Depends on D20270. Ref T10333. If you create a task with a new owner, or edit a task and change the priority/owner, we want to move it (and possibly create a new header) when the response comes back.

Make sure the response includes the appropriate details about the object's header and position.

Test Plan:
- Grouped by Owner.
- Created a new task with a new owner, saw the header appear.
- Edited a…