GCP allow to set global access on loadbalancer

The install config does not contain a way to set global access on the load balancer frontend config. This is needed when the installer runs inside a different region (ACM cluster from another region installs the gcp cluster).

Without global access the installer cannot connect to the api server (context exceeded).

2026-08-06T12:37:59.581558505Z installer time="2026-08-06T12:37:59Z" level=debug msg="E0806 12:37:59.580054     163 cluster_accessor.go:262] \"Connect failed\" err=\"error creating HTTP client and mapper: cluster
 is not reachable: Get \\\"https://api.gcp-demo.doman.name:6443/?timeout=5s\\\": context deadline exceeded\" controller=\"clustercache\" controllerGroup=\"cluster.x-k8s.io\" controllerKind=\"Cluster\" Cluster=\"openshift-cluster-api-guests/gcp-demo-c9swg\" namespace=\"openshift-cluster-api-guests
\" name=\"gcp-demo-c9swg\" reconcileID=\"95ee3214-f4ba-4bf7-8593-349f230c95d2\""                          2026-08-06T12:38:26.238445744Z installer time="2026-08-06T12:38:26Z" level=debug msg="Still waiting for the Kubernetes API: Get \"https://api.gcp-demo.doman.name:6443/version\": dial tcp <ip>:6443: i/o timeout"

If i set the global access flag after the loadbalancer is created the installer finishes.

Start by tracing how install configuration is translated into the GCP load balancer frontend configuration. Add support for setting global access, then verify that an installation from a different region can connect to the Kubernetes API server without timing out.