Automatic merge from submit-queue
Node authorizer
This PR implements the authorization portion of https://github.com/kubernetes/community/blob/master/contributors/design-proposals/kubelet-authorizer.md and kubernetes/features#279:
* Adds a new authorization mode (`Node`) that authorizes requests from nodes based on a graph of related pods,secrets,configmaps,pvcs, and pvs:
* Watches pods, adds edges (secret -> pod, configmap -> pod, pvc -> pod, pod -> node)
* Watches pvs, adds edges (secret -> pv, pv -> pvc)
* When both Node and RBAC authorization modes are enabled, the default RBAC binding that grants the `system:node` role to the `system:nodes` group is not automatically created.
* Tightens the `NodeRestriction` admission plugin to require identifiable nodes for requests from users in the `system:nodes` group.
This authorization mode is intended to be used in combination with the `NodeRestriction` admission plugin, which limits the pods and nodes a node may modify. To enable in combination with RBAC authorization and the NodeRestriction admission plugin:
* start the API server with `--authorization-mode=Node,RBAC --admission-control=...,NodeRestriction,...`
* start kubelets with TLS boostrapping or with client credentials that place them in the `system:nodes` group with a username of `system:node:<nodeName>`
```release-note
kube-apiserver: a new authorization mode (`--authorization-mode=Node`) authorizes nodes to access secrets, configmaps, persistent volume claims and persistent volumes related to their pods.
* Nodes must use client credentials that place them in the `system:nodes` group with a username of `system:node:<nodeName>` in order to be authorized by the node authorizer (the credentials obtained by the kubelet via TLS bootstrapping satisfy these requirements)
* When used in combination with the `RBAC` authorization mode (`--authorization-mode=Node,RBAC`), the `system:node` role is no longer automatically granted to the `system:nodes` group.
```
```release-note
RBAC: the automatic binding of the `system:node` role to the `system:nodes` group is deprecated and will not be created in future releases. It is recommended that nodes be authorized using the new `Node` authorization mode instead. Installations that wish to continue giving all members of the `system:nodes` group the `system:node` role (which grants broad read access, including all secrets and configmaps) must create an installation-specific ClusterRoleBinding.
```
Follow-up:
- [ ] enable e2e CI environment with admission and authorizer enabled (blocked by kubelet TLS bootstrapping enablement in https://github.com/kubernetes/kubernetes/pull/40760)
- [ ] optionally enable this authorizer and admission plugin in kubeadm
- [ ] optionally enable this authorizer and admission plugin in kube-up
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