Automatic merge from submit-queue (batch tested with PRs 51632, 51055, 51676, 51560, 50007)
GCE: Reserve address for ILBs during sync
**What this PR does / why we need it**:
This PR adds the ability for the service controller to hold the ILB's IP during sync which may delete/recreate the forwarding rule.
Fixes: #47531
**Release note**:
```release-note
GCE: Internal load balancer IPs are now reserved during service sync to prevent losing the address to another service.
```
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