Automatic merge from submit-queue

[Federation][join-01] Implement `kubefed join` command.

Supersedes PR #35155.

Please review only the last commit here. This is based on PR #35492 which will be reviewed independently.

I will add a release note separately for this entire feature, so please don't worry too much about the release note here in the PR.

Design Doc: PR #34484

cc @kubernetes/sig-cluster-federation @quinton-hoole @mwielgus