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/util/TokenUtils.java

@@ -33,7 +33,7 @@ public final class TokenUtils {
     private final String prefix;
     private final int length;
 
-    private TokenType(String prefix, int length) {
+    TokenType(String prefix, int length) {
       this.prefix = prefix;
       this.length = length;
     }