Automatic merge from submit-queue (batch tested with PRs 40943, 40967)

switch admission serialized config to an apiserver type

Switches the kube admission config from componentconfig to the new `apiserver.k8s.io` group so that all API servers can use the shared configuration.  This switch external serialization, but it does not move the code that reads the config.  I'd like to do that as a follow-on.

@kubernetes/sig-api-machinery-misc @kubernetes/api-reviewers @smarterclayton 
@derekwaynecarr ptal
@sttts