R1:91e5ca0ee28c

Merge the DrydockResource workers into a single worker

Summary:
Ref T9252. Currently, Drydock Leases and Resources have several workers:

- Resources: ResourceWorker, ResourceUpdateWorker, ResourceDestroyWorker
- Leases: AllocatorWorker, LeaseWorker, LeaseUpdateWorker, LeaseDestroyWorker

This is kind of a lot of stuff, and it creates some problems.

In particular, leases and resources in early lifecycle phases (pending/allocating/acquiring) can't process commands yet, because that code is only in the…