R1:09f3d0bb7ec0

Pass overseer configuration over stdin

Summary:
Ref T7352. This changes `phd` to pass configuration to overseers over stdin. We still run one overseer per daemon.

The "status" stuff needs some cleanup, but it's mostly just UI/cosmetic.

Test Plan:
- Ran `phd debug`, `phd launch`, `phd start`, `phd status`, `phd stop`, etc.
- Verified PID files write in a reasonable format.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7352

Differential Revision: https://secure.