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>.
Optimize admission plugin API requests
xref https://github.com/kubernetes/kubernetes/issues/63030#issuecomment-387774934
* resource changes are typically slow-moving, and full discovery can be slightly expensive, so this reduces the refresh to a 30 second interval and bumps QPS on the admission client (which wasn't done when the client started getting used for discovery in #62659)
* a large consumer of API requests in scale tests was the node restriction plugin pod lookups during pod deletion. this switches to use the same informer that is feeding the node authorizer graph to avoid those lookups entirely.
```release-note
NONE
```
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