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/output.tf

@@ -0,0 +1,23 @@
+output "proxy_name_servers" {
+  value = "${google_dns_managed_zone.proxy_domain.name_servers}"
+}
+
+output "proxy_instance_groups" {
+  value = "${local.proxy_instance_groups}"
+}
+
+output "proxy_service_account" {
+  value = {
+    email     = "${google_service_account.proxy_service_account.email}"
+    client_id = "${google_service_account.proxy_service_account.unique_id}"
+  }
+}
+
+output "proxy_ip_addresses" {
+  value = {
+    ipv4        = "${module.proxy_networking.proxy_ipv4_address}"
+    ipv6        = "${module.proxy_networking.proxy_ipv6_address}"
+    ipv4_canary = "${module.proxy_networking_canary.proxy_ipv4_address}"
+    ipv6_canary = "${module.proxy_networking_canary.proxy_ipv6_address}"
+  }
+}