R1:a3518e19a565

Merge GC daemon into Trigger daemon

Summary:
Fixes T7352. This reduces the memory footprint for instances by combining these two similar daemons into one daemon which handles the responsibilities of both.

The fit isn't 100% perfect here but it's pretty close, and the GC daemon is fairly trivial.

Test Plan:
- Adjusted all the numbers to small numbers (5 second sleep, 120 second GC length).
- Added a ton of logging.
- Started trigger daemon.
- Saw it run a GC cycle.
- Saw it reschedule…