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/gcs.tf

@@ -0,0 +1,10 @@
+resource "google_storage_bucket" "proxy_certificate" {
+  name          = "${var.proxy_certificate_bucket}"
+  storage_class = "MULTI_REGIONAL"
+}
+
+resource "google_storage_bucket_iam_member" "member" {
+  bucket = "${google_storage_bucket.proxy_certificate.name}"
+  role   = "roles/storage.objectViewer"
+  member = "serviceAccount:${google_service_account.proxy_service_account.email}"
+}