R1:4ac82be5ed22

Merge the DrydockLease workers into a single worker

Summary:
Ref T9252. This is the same as D14201, but for lease stuff instead of resource stuff.

This one is a little heavier but still feels pretty reasonable to me at the end of the day (worker is <1K lines and has a ton of comment stuff).

Also fixes a few random bugs I hit in the task queue.

Test Plan:
- Restarted some Harbormaster builds, saw them go through cleanly.
- Released pre-activation resources/leases.
- Probably still kinda buggy but…