Automatic merge from submit-queue (batch tested with PRs 46407, 46457)

GCE - Refactor API for firewall and backend service creation

**What this PR does / why we need it**:
 - Currently, firewall creation function actually instantiates the firewall object; this is inconsistent with the rest of GCE api calls. The API normally gets passed in an existing object.
 - Necessary information for firewall creation, (`computeHostTags`,`nodeTags`,`networkURL`,`subnetworkURL`,`region`) were private to within the package. These now have public getters.
 - Consumers might need to know whether the cluster is running on a cross-project network. A new `OnXPN` func will make that information available.
 - Backend services for regions have been added. Global ones have been renamed to specify global. 
 - NamedPort management of instance groups has been changed from an `AddPortsToInstanceGroup` func (and missing complementary `Remove...`) to a single, simple `SetNamedPortsOfInstanceGroup`
 - Addressed nitpick review comments of #45524 

ILB needs the regional backend services and firewall refactor.  The ingress controller needs the new `OnXPN` func to decide whether to create a firewall.

**Release note**:
```release-note
NONE
```