Automatic merge from submit-queue (batch tested with PRs 45453, 45307, 44987)

[Federation] Add a worker queue to the generic sync controller.

This is in preparation for converting the ReplicaSet controller to be a generic sync controller.

This doesn't include support for multiple workers yet: it's not immediately obvious how to support the command-line flags for ReplicaSet (or, I suppose in general, how do TypeAdapters support external configuration via whatever flag mechanism we're using).

cc @marun

**Release note**:
```release-note
NONE
```