text: Title: UPSTREAM: 53446: kubelet: add latency metrics to network plugin manager
  Body: https://github.com/kubernetes/kubernetes/pull/53446
  
  Right now, we can't account for all the time spent in the PLEG loop.  We have `kubelet_docker_operations_latency_microseconds` to account for container runtime delays but nothing to capture delays due to the CNI plugin.  This PR adds those metrics.
  
  xref https://bugzilla.redhat.com/show_bug.cgi?id=1486914
  
  @smarterclayton @eparis @smarterclayton @jeremyeder @DirectXMan12 @dcbw 
  
  Adding do-not-merge until rebase completes.