Clean up some code quality issues

This removes some qualifiers that aren't necessary (e.g. public/abstract on interfaces, private on enum constructors, final on private methods, static on nested interfaces/enums), uses Java 8 lambdas and features where that's an improvement

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=177182945

java/google/registry/model/eppcommon/ProtocolDefinition.java

@@ -95,8 +95,11 @@ public class ProtocolDefinition {
     }
   }
 
-  /** Converts a service extension enum to its URI. */
-  /** This stores a map from URI back to the service extension enum. */
+  /**
+   * Converts a service extension enum to its URI.
+   *
+   *  <p>This stores a map from URI back to the service extension enum.
+   */
   private static final ImmutableMap<String, ServiceExtension> serviceExtensionByUri =
       uniqueIndex(EnumSet.allOf(ServiceExtension.class), ServiceExtension::getUri);