Automatic merge from submit-queue (batch tested with PRs 55594, 47849, 54692, 55478, 54133). 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 kubeadm alpha phase kubeconfig option(--output)

**What this PR does / why we need it**:
This PR will add --output option to `kubeadm alpha phase kubeconfig [command]`
This option can change output directory of kubeconfig.

Prev: kubeadm alpha phase kubeconfig admin
  we can get admin.conf in /etc/kubernetes/ .

This PR: kubeadm alpha phase kubeconfig admin --output /root
  we can get admin.conf in /root/ .

Of course, --output is optional.(default directory is /etc/kubernetes)

Note)
  I have no confidence about my test code.

Thank you.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
```