Automatic merge from submit-queue (batch tested with PRs 51229, 50131, 51074, 51167, 51213)
[proxy] Clean up LocalPort related functions and structures in proxier.go
**What this PR does / why we need it**:
See, https://github.com/kubernetes/kubernetes/blob/master/pkg/proxy/iptables/proxier.go#L1694
I think RevertPorts() is independent from iptables, and would be used by other proxiers which needs to hold/close local port.
Perhaps we can move RevertPorts() from proxier.go to pkg/proxy/util package so that it can be consumed among different proxiers. And, reduce codes in proxier.go
**Which issue this PR fixes**:
fixes#51073
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
c358544e83