Automatic merge from submit-queue

Convert HPA controller to support HPA v2 mechanics

This PR converts the HPA controller to support the mechanics from HPA v2.
The HPA controller continues to make use of the HPA v1 client, but utilizes
the conversion logic to work with autoscaling/v2alpha1 objects internally.

It is the follow-up PR to #36033 and part of kubernetes/features#117.

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