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>.
admission: wire through validating-only admission
Based on https://github.com/kubernetes/kubernetes/pull/54232.
This is important and required for beta because it affects the shape of the webhook admission plugins that are going to be produced and is needed to make sure that our existing chain continues to properly verify and protect the API objects based on their final state after webhook admission mutators run.
We discussed this in the October 11 API machinery call with @erictune and @caesarxuchao and we agreed to do this as a requirement for beta. See this part of the recording: https://www.youtube.com/watch?v=mrgDPHyr4VY#t=325 .
Handle failure cases on startup gracefully to avoid causing cascading
errors and poor initialization in other components. Initial errors from
config load cause the initializer to pause and hold requests. Return
typed errors to better communicate failures to clients.
Add code to handle two specific cases - admin wants to bypass
initialization defaulting, and mirror pods (which want to bypass
initialization because the kubelet owns their lifecycle).
Kubernetes Submit Queue