Fix a bug in type hierarchy marking in the trimmer (#86635)

Fix a bug in type hierarchy marking in the trimmer (#86635)

If the base class has DAM annotation on it, but the only access is through a variabled typed as the derived class, the marking of everything on the base class happens during the processing of the derived class.

The bug was that it would only apply marking for the difference in effective annotations between derived and base, so if the annotation is on base, then both have effectively the same annotation and there would be no additional marking on base. So for example private methods would not be marked.

This also affected warnings on virtual methods - see tests for more details.