Automatic merge from submit-queue (batch tested with PRs 55360, 56444, 56687, 56791, 56802). 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>.
kube-apiserver: enable admissionregistration v1beta1 api by default
We have this enabled in the GCE cluster and in local-cluster-up, but forgot to switch the default. If we want people to use this feature by default in production clusters, we better enable the API.
Moreover, this PR fixes that beta works without alpha.
```release-note
Enable admissionregistration.k8s.io/v1beta1 by default in kube-apiserver.
```
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