Automatic merge from submit-queue

[GarbageCollector] Let the RC manager set/remove ControllerRef

What's done:
* RC manager sets Controller Ref when creating new pods
* RC manager sets Controller Ref when adopting pods with matching labels but having no controller
* RC manager clears Controller Ref when pod labels change
* RC manager clears pods' Controller Ref when rc's selector changes
* RC manager stops adoption/creating/deleting pods when rc's DeletionTimestamp is set
* RC manager bumps up ObservedGeneration: The [original code](https://github.com/kubernetes/kubernetes/blob/master/pkg/controller/replication/replication_controller_utils.go#L36) will do this.
* Integration tests:
  * verifies that changing RC's selector or Pod's Labels triggers adoption/abandoning
* e2e tests (separated to #27151):
  * verifies GC deletes the pods created by RC if DeleteOptions.OrphanDependents=false, and orphans the pods if DeleteOptions.OrphanDependents=true.

TODO:

- [x] we need to be able to select Pods that have a specific ControllerRef. Then each time we sync the RC, we will iterate through all the Pods that has a controllerRef pointing the RC, event if the labels of the Pod doesn't match the selector of RC anymore. This will prevent a Pod from stuck with a stale controllerRef, which could be caused by the race between abandoner (the goroutine that removes controllerRef) and worker the goroutine that add controllerRef to pods).
- [ ] use controllerRef instead of calling `getPodController`. This might be carried out by the control-plane team.
- [ ] according to the controllerRef proposal (#25256): "For debugging purposes we want to add an adoptionTime annotation prefixed with kubernetes.io/ which will keep the time of last controller ownership transfer." This might be carried out by the control-plane team.

cc @lavalamp @gmarek