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/tldconfig/idn/IdnTableEnum.java

@@ -29,7 +29,7 @@ public enum IdnTableEnum {
 
   private final IdnTable table;
 
-  private IdnTableEnum() {
+  IdnTableEnum() {
     this.table = load(Ascii.toLowerCase(name()));
   }