Automatic merge from submit-queue. 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>.

Introduce PodSecurityPolicy in the policy/v1beta1 API group

Types/constants are completely the same as in `extensions/v1beta1` except that they are located outside of the `extensions` API group.

**What this PR does / why we need it**:
This is the first step for migrating PSP-related stuff away of `extensions` group. See #43214 for more information.

Also it related to https://github.com/kubernetes/features/issues/5

**Example**:
```console
$ cat restricted2.yaml 
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: restricted2
...
$ kubectl create -f restricted.yaml 
podsecuritypolicy "restricted2" created
$ kubectl get psp restricted2 -o yaml
apiVersion: extensions/v1beta1
kind: PodSecurityPolicy
...
```

**Release note**:
```release-note
The `PodSecurityPolicy` API has been moved to the `policy/v1beta1` API group. The `PodSecurityPolicy` API in the `extensions/v1beta1` API group is deprecated and will be removed in a future release.
```