R1:ef22fe1e743c

Add a --force command to `phd start`

Summary:
Ref T7352. This isn't wildly useful for us but seems generally reasonable, can be helpful with testing, and @hach-que has a use case for it.

The only reason we issue this warning is to prevent user error; you can still launch all the daemons with `phd launch` manually and daemons all use locks to protect critical regions.

Test Plan: Ran `phd start --force` a bunch, saw zillions of daemons.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley…