Use terraform to config GCP proxy setup

With terraform (https://terraform.io) we can convert most of the infrastructure setup into code. This simplifies setting up a new proxy as well as providing reproducibility in the setup, eliminating human errors as much as possible.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=190634711

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

@@ -0,0 +1,16 @@
+variable "proxy_service_account_email" {}
+
+variable "proxy_cluster_region" {}
+
+variable "proxy_cluster_zones" {
+  type = "map"
+  default = {
+    americas = "us-east4-a"
+    emea = "europe-west4-b"
+    apac = "asia-northeast1-c"
+  }
+}
+
+variable "proxy_ports" {
+  type = "map"
+}