gcp: rename gcp-zone to region

Following the previous commits, updated GCP zone naming for consistency:

AWS:   -aws-region
Azure: -region
GCP:   -zone

GCP is using zones instead of regions, since IBM is also without prefix,
I'm joing the non-prefix team here.

Signed-off-by: Beraldo Leal <bleal@redhat.com>

src/cloud-api-adaptor/entrypoint.sh

@@ -96,7 +96,7 @@ gcp() {
 
     [[ "${PODVM_IMAGE_NAME}" ]] && optionals+="-image-name ${PODVM_IMAGE_NAME} "
     [[ "${GCP_PROJECT_ID}" ]] && optionals+="-gcp-project-id ${GCP_PROJECT_ID} "
-    [[ "${GCP_ZONE}" ]] && optionals+="-gcp-zone ${GCP_ZONE} "                         # if not set retrieved from IMDS
+    [[ "${GCP_ZONE}" ]] && optionals+="-zone ${GCP_ZONE} "                         # if not set retrieved from IMDS
     [[ "${GCP_MACHINE_TYPE}" ]] && optionals+="-machine-type ${GCP_MACHINE_TYPE} "     # default e2-medium
     [[ "${GCP_NETWORK}" ]] && optionals+="-network ${GCP_NETWORK} "                # defaults to 'default'
 

src/cloud-providers/gcp/manager.go

@@ -21,7 +21,7 @@ func (_ *Manager) ParseCmd(flags *flag.FlagSet) {
 
 	flags.StringVar(&gcpcfg.GcpCredentials, "gcp-credentials", "", "Google Application Credentials, defaults to `GCP_CREDENTIALS`")
 	flags.StringVar(&gcpcfg.ProjectId, "gcp-project-id", "", "GCP Project ID")
-	flags.StringVar(&gcpcfg.Zone, "gcp-zone", "", "Zone")
+	flags.StringVar(&gcpcfg.Zone, "zone", "", "Zone")
 	flags.StringVar(&gcpcfg.ImageName, "image-name", "", "Pod VM image name")
 	flags.StringVar(&gcpcfg.MachineType, "machine-type", "e2-medium", "Pod VM instance type")
 	flags.StringVar(&gcpcfg.Network, "network", "", "Network ID to be used for the Pod VMs")