text: Title: Update namespace controller to use the metadata client
  Body: The namespace controller currently uses dynamic client and JSON to perform operations only on resource metadata. This PR changes the namespace controller to use the metadata client - a client that uses the server-side conversion logic to retrieve only the metadata about the object in protobuf - to more efficiently interact with the server.
  
  Built on #77819 and #78743 
  
  Part of https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/20190322-server-side-get-to-ga.md
  
  /kind cleanup
  
  ```release-note
  The namespace controller has been updated to use the metadata client which improves memory
  and CPU usage of the Kube controller manager.
  ```