NewControllerExpectations returns a store for ControllerExpectations.

If a watch drops a delete event for a pod, it'll take this long before a dormant controller waiting for those packets is woken up anyway.

ExpKeyFunc to parse out the key from a ControlleeExpectation.

ControlleeExpectations track controllee creates/deletes.

ControllerExpectations is a cache mapping controllers to what they expect to see before being woken up for a sync.

Expectations are either fulfilled, or expire naturally.