Automatic merge from submit-queue (batch tested with PRs 62425, 62212, 60824, 62383, 62384). 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>.
Clean up the network plugin code
Moves the `pkg/kubelet/network` package down to `dockershim` since network
setup is done by the runtime. Also remove various interfaces/code added only for
backward compatibility with non-CRI runtimes, which are now removed from the
codebase.
**Release note**:
```release-note
NONE
```
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