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