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/iam.tf

@@ -0,0 +1,20 @@
+resource "google_service_account" "proxy_service_account" {
+  account_id   = "proxy-service-account"
+  display_name = "Nomulus proxy service account"
+}
+
+resource "google_project_iam_member" "gcr_storage_viewer" {
+  project = "${var.gcr_project_name}"
+  role    = "roles/storage.objectViewer"
+  member  = "serviceAccount:${google_service_account.proxy_service_account.email}"
+}
+
+resource "google_project_iam_member" "metric_writer" {
+  role   = "roles/monitoring.metricWriter"
+  member = "serviceAccount:${google_service_account.proxy_service_account.email}"
+}
+
+resource "google_project_iam_member" "log_writer" {
+  role   = "roles/logging.logWriter"
+  member = "serviceAccount:${google_service_account.proxy_service_account.email}"
+}