Automatic merge from submit-queue (batch tested with PRs 66121, 66140, 66045). 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>.
Allow modifying current context with kubectl set-context
Fixes https://github.com/kubernetes/kubernetes/issues/40968
Enabled setting the namespace (or any other attribute) for the current context, rather than needing to provide a name:
```
kubectl config set-context --current --namespace=some-namespace
kubectl config set-context --current --cluster=some-cluster
kubectl config set-context --current --user=some-user
```
```release-note
`kubectl config set-context` can now set attributes of the current context, like the current namespace, by passing `--current` instead of a specific context name
```
43d30a143b