Automatic merge from submit-queue (batch tested with PRs 56128, 56004, 56083, 55833, 56042). 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>.

Graduate the admission and admissionregistration (webhook part) API to v1beta1

ref: kubernetes/features#492

Most changes are mechanical. Please take a look at the commit message to see if the commit is worth reviewing.

```release-note
Action required:
The `admission/v1alpha1` API has graduated to `v1beta1`. Please delete your existing webhooks before upgrading the cluster, and update your admission webhooks to use the latest API, because the API has backwards incompatible changes.
The webhook registration related part of the `admissionregistration` API has graduated to `v1beta1`. Please delete your existing configurations before upgrading the cluster, and update your configuration file to use the latest API.
```