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>.

cluster: remove salt

Nothing uses it directly. There were some dangling dependencies from GCE and Centos kube-ups, so I just copied them into respective dirs.

see #49213

```release-note
Remove deprecated and unmaintained salt support. kubernetes-salt.tar.gz will no longer be published in the release tarball.
```