Make PrologEnvironment ~6500% faster

Instead of passing the Injector use a singleton Args object that wraps
up all of the singletons needed in prolog predicates.

This offers less flexibility to plugin predicates but gets rid of a
potential Guice problem.  The claimed performance difference may not
exist, but a warning message is removed on startup.

Change-Id: Iceba5d4fb7f75eb867c6a968e5f43912e2213837

gerrit-server/src/main/java/gerrit/PRED_current_user_2.java

@@ -112,7 +112,6 @@ class PRED_current_user_2 extends Predicate.P2 {
   }
 
   private static IdentifiedUser.GenericFactory userFactory(Prolog engine) {
-    PrologEnvironment env = (PrologEnvironment) engine.control;
-    return env.getInjector().getInstance(IdentifiedUser.GenericFactory.class);
+    return ((PrologEnvironment) engine.control).getArgs().getUserFactory();
   }
 }