Add configs for production GCP proxy

This also introduces a production canary environment, similar to sandbox canary. The docker tags are changed to "live" and "sandbox" respectively, to reflect the fact that different images may be used for prod and sandbox.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=204343530

java/google/registry/proxy/ProxyConfig.java

@@ -25,6 +25,7 @@ public class ProxyConfig {
 
   enum Environment {
     PRODUCTION,
+    PRODUCTION_CANARY,
     SANDBOX,
     SANDBOX_CANARY,
     ALPHA,