Drive "phd stop" entirely from the process list, not PID files on disk
Summary:
Ref T13321. Depends on D20600. Make `bin/phd stop` mean:
- `bin/phd stop`: Stop all processes which have daemon process titles. If we're instanced, only stop daemons for the current instance.
- `bin/phd stop --force`: Stop all processes which have deamon process titles for any instance.
We no longer read or care about PID files on disk, and this moves us away from PID files.
This makes unusual flag `--gently` do nothing. A followup will update the documentation and flags to reflect actual usage/behavior.
This also removes the ability to stop specific PIDs. This was somewhat useful long, long ago when you might explicitly run different copies of the `PullLocal` daemon with flags to control which repositories they updated, but with the advent of clustering it's no longer valid to run custom daemon loadouts.
Test Plan: Ran `bin/phd start`, then `bin/phd stop`. Saw instance daemons stop. Ran `bin/phd stop --force`, saw all daemons stop.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13321
Differential Revision: https://secure.phabricator.com/D20601