Automatic merge from submit-queue
[Federation][init] Implement `kubefed init` command that performs federation control plane bootstrap.
Please review only the last commit here. This is based on PR #35593 which will be reviewed independently.
I am intentionally not including the unit tests in this PR to better distribute and parallelize reviews. This PR is already big.
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 @nikhiljindal
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