Automatic merge from submit-queue (batch tested with PRs 64013, 63896, 64139, 57527, 62102). 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>.
add dynamic config metrics
This PR exports config-releated metrics from the Kubelet.
The Guages for active, assigned, and last-known-good config can be used
to identify config versions and produce aggregate counts across several
nodes. The error-reporting Gauge can be used to determine whether a node
is experiencing a config-related error, and to prodouce an aggregate
count of nodes in an error state.
https://github.com/kubernetes/features/issues/281
```release-note
The Kubelet now exports metrics that report the assigned (node_config_assigned), last-known-good (node_config_last_known_good), and active (node_config_active) config sources, and a metric indicating whether the node is experiencing a config-related error (node_config_error). The config source metrics always report the value 1, and carry the node_config_name, node_config_uid, node_config_resource_version, and node_config_kubelet_key labels, which identify the config version. The error metric reports 1 if there is an error, 0 otherwise.
```
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