Automatic merge from submit-queue (batch tested with PRs 39435, 39454)
Fix PDB by percentages for StatefulSet pods
Previously, PDBs defined in terms of percentages would error out with StatefulSet as they did not know how to find the scale associated.
This change teaches the disruption controller to also look at StatefulSets and their scale.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes https://github.com/kubernetes/kubernetes/issues/39125
**Release note**:
```release-note
Fix issue with PodDisruptionBudgets in which `minAvailable` specified as a percentage did not work with StatefulSet Pods.
```
cc @a-robinson @kow3ns @kubernetes/sig-apps-misc
f8b708385e