Remove commitAdditionalLogicChanges(), part 1

Now that the flows are flattened, the commitAdditionalLogicChanges() call, which used to come later in the flow to actually save the Datastore objects, is now happening right after the performAdditionalXXXLogic() call. So we can instead just do the saves in performAdditionalXXXLogic(), and get rid of the separate call. As a first step, this CL simply makes commitAdditionalLogicChanges() a private method that gets called internally by the extra logic manager. Later, we can move the saves into their proper position, affecting only the extra logic class itself.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=137529991

java/google/registry/flows/domain/DomainUpdateFlow.java

@@ -333,7 +333,6 @@ public final class DomainUpdateFlow extends Flow implements TransactionalFlow {
     if (extraFlowLogic.isPresent()) {
       extraFlowLogic.get().performAdditionalDomainUpdateLogic(
           existingDomain, clientId, now, eppInput, historyEntry);
-      extraFlowLogic.get().commitAdditionalLogicChanges();
     }
   }
 }