Add Interface.isLocal and use it where appropriate

Some EJB logic regrettably needs to be renamed out of the way. Hopefully the churn caused by this is less than would be caused if Interface's isLocal needed to be named differently from Class.isLocal.

java/ql/src/utils/Stubs.qll

@@ -8,15 +8,10 @@
 import java
 
 /** A type that should be in the generated code. */
-abstract private class GeneratedType extends RefType {
+abstract private class GeneratedType extends ClassOrInterface {
   GeneratedType() {
-    (
-      this instanceof Interface
-      or
-      this instanceof Class
-    ) and
     not this instanceof AnonymousClass and
-    not this instanceof LocalClass and
+    not this.isLocal() and
     not this.getPackage() instanceof ExcludedPackage
   }