R1:de70a4ff267e

Improve consistency in use of "via", "objectPHID", and "containerPHID" parameters in repository workers

Summary:
Ref T13591. Improve how parameters are passed between commit worker tasks:

- Always pass "via", to track where tasks came from.
- Always provide "objectPHID" (with the commit PHID).
- Always provide "containerPHID" (with the repository PHID).

Test Plan:
- Pushed a new commit.
- Ran `bin/repository pull` + `bin/repository discover`, saw commit with all parameters.
- Ran `bin/worker…