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/batch/DeleteProberDataAction.java

@@ -138,7 +138,7 @@ public class DeleteProberDataAction implements Runnable {
         if (proberRoidSuffixes.contains(roidSuffix)) {
           deleteDomain(key);
         } else {
-          getContext().incrementCounter(String.format("skipped, non-prober data"));
+          getContext().incrementCounter("skipped, non-prober data");
         }
       } catch (Throwable t) {
         logger.severefmt(t, "Error while deleting prober data for key %s", key);