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

javatests/google/registry/proxy/quota/testdata/quota_config_default.yaml

@@ -0,0 +1,8 @@
+refreshSeconds: 3600
+
+defaultQuota:
+  userId: []
+  tokenAmount: 100
+  refillSeconds: 60
+
+customQuota: []

javatests/google/registry/proxy/quota/testdata/quota_config_duplicate.yaml

@@ -0,0 +1,14 @@
+refreshSeconds: 3600
+
+defaultQuota:
+  userId: []
+  tokenAmount: 100
+  refillSeconds: 60
+
+customQuota:
+  - userId: ["abc", "def"]
+    tokenAmount: 10
+    refillSeconds: 60
+  - userId: ["xyz123", "def", "luckycat"]
+    tokenAmount: 500
+    refillSeconds: 10

javatests/google/registry/proxy/quota/testdata/quota_config_no_refresh_no_refill.yaml

@@ -0,0 +1,8 @@
+refreshSeconds: 0
+
+defaultQuota:
+  userId: []
+  tokenAmount: 100
+  refillSeconds: 0
+
+customQuota: []

javatests/google/registry/proxy/quota/testdata/quota_config_regular.yaml

@@ -0,0 +1,14 @@
+refreshSeconds: 3600
+
+defaultQuota:
+  userId: []
+  tokenAmount: 100
+  refillSeconds: 60
+
+customQuota:
+  - userId: ["abc", "def"]
+    tokenAmount: 10
+    refillSeconds: 60
+  - userId: ["xyz123", "987lol", "luckycat"]
+    tokenAmount: 500
+    refillSeconds: 10

javatests/google/registry/proxy/quota/testdata/quota_config_unlimited_tokens.yaml

@@ -0,0 +1,8 @@
+refreshSeconds: 3600
+
+defaultQuota:
+  userId: []
+  tokenAmount: -1
+  refillSeconds: 60
+
+customQuota: []