Rework "next sync time" logic

[John Strunk]

Describe the bug

• Rework logic for next sync time to:
  • Perform a sync immediately
  • Properly update the schedule (immediately) if trigger.schedule is changed
  • Do better about determining whether we are "waiting for next" or "trying to sync" when reconciling

Also fix the situation where sometimes the Job doesn't get cleaned up at the end of an interval.

Steps to reproduce

Expected behavior

Actual results

Additional context