Automatic merge from submit-queue (batch tested with PRs 46252, 45524, 46236, 46277, 46522)
Add /healthz back to kube-proxy metrics server
Fixes#46447.
/healthz is removed from kube-proxy metrics server by #44968 and that breaks our upgrade test, which run 1.6 tests on 1.7 cluster. It seems harmless to continue holding /healthz on metrics server as well, so that we won't break other potential users.
/assign @bowei
cc @dchen1107
**Release note**:
```release-note
NONE
```
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