Automatic merge from submit-queue (batch tested with PRs 39260, 40216, 40213, 40325, 40333)

genericapiserver: more dependency cutoffs

- cut-off pkg/api.Resource and friends - lgtm
- authn plugins -> k8s.io/apiserver - 
- webhook authz plugin -> k8s.io/apiserver - lgtm
- ~~pkg/cert -> k8s.io/apimachinery (will rebase on @deads2k's PR also moving it)~~
- split pkg/config into kubelet config merger and flags - lgtm
- split feature gate between generic apiserver and kube - lgtm
- move pkg/util/flag into k8s.io/apiserver - lgtm