Automatic merge from submit-queue (batch tested with PRs 66822, 65983). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
apiextensions-apiserver: enable etcd_object_count metrics for CustomResources
~~This leaks one go routine per CRD that is deleted~~ The stop channel is wired already. We should not have the leak of the go routine:
d10e08fc89/staging/src/k8s.io/apiserver/pkg/registry/generic/registry/store.go (L1379)
```release-note
Added etcd_object_count metrics for CustomResources.
```