Move GCP proxy code to the old [] proxy's location

1. Moved code for the GCP proxy to where the [] proxy code used to live.
3. Corrected reference to the GCP proxy location.
4. Misc changes to make ErrorProne and various tools happy.

+diekmann to LGTM terraform whitelist change.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213630560

java/google/registry/proxy/terraform/modules/gke.tf

@@ -0,0 +1,25 @@
+module "proxy_gke_americas" {
+  source                      = "./gke"
+  proxy_cluster_region        = "americas"
+  proxy_service_account_email = "${google_service_account.proxy_service_account.email}"
+}
+
+module "proxy_gke_emea" {
+  source                      = "./gke"
+  proxy_cluster_region        = "emea"
+  proxy_service_account_email = "${google_service_account.proxy_service_account.email}"
+}
+
+module "proxy_gke_apac" {
+  source                      = "./gke"
+  proxy_cluster_region        = "apac"
+  proxy_service_account_email = "${google_service_account.proxy_service_account.email}"
+}
+
+locals {
+  "proxy_instance_groups" = {
+    americas = "${module.proxy_gke_americas.proxy_instance_group}"
+    emea     = "${module.proxy_gke_emea.proxy_instance_group}"
+    apac     = "${module.proxy_gke_apac.proxy_instance_group}"
+  }
+}