Automatic merge from submit-queue (batch tested with PRs 54493, 52501, 55172, 54780, 54819). 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>.
Add CoreDNS as feature in kubeadm
**What this PR does / why we need it**:
This PR adds CoreDNS as a DNS plugin via the feature-gate option in Kubeadm init.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*:
Fixeskubernetes/features#427
**Special notes for your reviewer**:
**Release note**:
```release-note
kubeadm: Add an experimental mode to deploy CoreDNS instead of KubeDNS
```
/cc @johnbelamaric
d42be07e08