Automatic merge from submit-queue (batch tested with PRs 66138, 65951). 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>.

Don't validate HealthzBindAddress in KubeProxyConfiguration if it's empty

**What this PR does / why we need it**:
https://github.com/kubernetes/kubernetes/pull/49087 added validation for
the HealthzBindAddress field in the KubeProxyConfiguration, but if you pass in
--healthz-port=0 to the kube-proxy CLI, it sets this field to the empty string.
However, an empty string is not a valid value for this field.

This change allows validation to pass if HealthzBindAddress is empty.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Ref #65118

**Special notes for your reviewer**:

**Release note**:

```release-note
Fix validation for HealthzBindAddress in kube-proxy when --healthz-port is set to 0
```