Automatic merge from submit-queue (batch tested with PRs 41994, 41969, 41997, 40952, 40576)
Guaranteed admission for Critical Pods
This is the first step in implementing node-level preemption for critical pods.
It defines the AdmissionFailureHandler interface, which allows callers, like the kubelet, to define how failed predicates are handled, and take steps to correct failures if necessary.
In the kubelet's implementation, it triggers preemption if the pod being admitted is critical, and if the only failed predicates are InsufficientResourceErrors, then it prempts (not yet implemented) other other pods to allow admission of the critical pod.
cc: @vishh
16f87fe7d8