update tests
add comment
amend var name
update comment
add check for empty slice
fix tests
fix mask size in test
review feedback
add ipv4 and ipv6 flag for mask sizes
add to violation exception list
remove import alias
run update-openapi-spec
review feedback
run update-bazel
review feedback
review feedback
**What type of PR is this?**
/kind cleanup
**What this PR does / why we need it**:
Staging the GCE Cloud Provider as part of KEP [20190125-removing-in-tree-providers](https://github.com/kubernetes/enhancements/blob/master/keps/sig-cloud-provider/20190125-removing-in-tree-providers.md). Staging repo setup here https://github.com/kubernetes/legacy-cloud-providers
Moves the GCE cloud provider implementation to staging.
This is in preparation for moving the cloud provider code out of tree entirely.
However we need it in staging while the code needs to be consumed both in/out of tree.
**Which issue(s) this PR fixes**:
Fixes #
**Special notes for your reviewer**:
**Does this PR introduce a user-facing change?**:
```
NONE
```
Updated import dependency tracking.
Factored in the cleanup from #77412
Minor fix to go.mod.
clusterCIDR is passed down from kube_env CLUSTER_IP_RANGE to the flag --cluster-cidr.
We plan not to let GKE to pass down CLUSTER_IP_RANGE to kube-env for the master node.
