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/model/domain/DomainCommand.java

@@ -67,7 +67,7 @@ public class DomainCommand {
    */
   public interface CreateOrUpdate<T extends CreateOrUpdate<T>> extends SingleResourceCommand {
     /** Creates a copy of this command with hard links to hosts and contacts. */
-    public T cloneAndLinkReferences(DateTime now) throws InvalidReferencesException;
+    T cloneAndLinkReferences(DateTime now) throws InvalidReferencesException;
   }
 
   /** The fields on "chgType" from {@link "http://tools.ietf.org/html/rfc5731"}. */

java/google/registry/model/domain/fee/FeeCheckCommandExtension.java

@@ -38,9 +38,9 @@ public interface FeeCheckCommandExtension<
    *
    * <p>Returns null if this version of the fee extension doesn't specify currency at the top level.
    */
-  public CurrencyUnit getCurrency();
+  CurrencyUnit getCurrency();
 
-  public ImmutableSet<C> getItems();
+  ImmutableSet<C> getItems();
 
-  public R createResponse(ImmutableList<? extends FeeCheckResponseExtensionItem> items);
+  R createResponse(ImmutableList<? extends FeeCheckResponseExtensionItem> items);
 }

java/google/registry/model/domain/fee/FeeCheckResponseExtension.java

@@ -31,7 +31,7 @@ public interface FeeCheckResponseExtension<F extends FeeCheckResponseExtensionIt
    * If currency is not supported at the top level of Check responses for this version of the fee
    * extension, this function has not effect.
    */
-  public void setCurrencyIfSupported(CurrencyUnit currency);
+  void setCurrencyIfSupported(CurrencyUnit currency);
 
-  public ImmutableList<F> getItems();
+  ImmutableList<F> getItems();
 }

java/google/registry/model/domain/launch/LaunchPhase.java

@@ -68,7 +68,7 @@ public class LaunchPhase extends ImmutableObject {
   /**
    * Returns a map of the static final fields to their values, case-converted.
    */
-  private static final ImmutableMap<String, LaunchPhase> initEnumMapping() {
+  private static ImmutableMap<String, LaunchPhase> initEnumMapping() {
     ImmutableMap.Builder<String, LaunchPhase> builder = new ImmutableMap.Builder<>();
     for (Entry<String, LaunchPhase> entry : getTypesafeEnumMapping(LaunchPhase.class).entrySet()) {
       builder.put(UPPER_UNDERSCORE.to(LOWER_CAMEL, entry.getKey()), entry.getValue());