Automatic merge from submit-queue (batch tested with PRs 40796, 40878, 36033, 40838, 41210)
HPA v2 (API Changes)
**Release note**:
```release-note
Introduces an new alpha version of the Horizontal Pod Autoscaler including expanded support for specifying metrics.
```
Implements the API changes for kubernetes/features#117.
This implements #34754, which is the new design for the Horizontal Pod Autoscaler. It includes improved support for custom metrics (and/or arbitrary metrics) as well as expanded support for resource metrics. The new HPA object is introduces in the API group "autoscaling/v1alpha1".
Note that the improved custom metric support currently is limited to per pod metrics from Heapster -- attempting to use the new "object metrics" will simply result in an error. This will change once #34586 is merged and implemented.
45d122dd6b