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

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

java/google/registry/whois/WhoisResponse.java

@@ -37,7 +37,7 @@ public interface WhoisResponse {
 
   /** A wrapper class for the plaintext response of a WHOIS command and its number of results. */
   @AutoValue
-  abstract static class WhoisResponseResults {
+  abstract class WhoisResponseResults {
     public abstract String plainTextOutput();
     public abstract int numResults();