R1:9e0a299b06c3

Launch daemons with a full Phabricator environment in the overseers

Summary:
Ref T1670. Prepare for the overseers to talk directly to the database instead of using Conduit. See T1670 for discussion.

This shouldn't impact anything, except it has a very small chance of destabilizing the overseers.

Test Plan:
Ran `phd launch`, `phd debug`, `phd start`.

Ran with `--trace-memory` and verified elevated but mostly steady memory usage (8MB / overseer). This climbed by 0.05KB / sec (4MB / day) but the source of…