[Checkers] Class supertypes and interfaces

[Matt Papi]

> they still have the same problem as they all call fromTreeWithVisitor() 
> which calls annotateImplicit() which goes ahead and adds 
> implicit/default annotations. 

While writing the patch, I had some trouble in at least one place not 
having some of the methods call annotateImplicit(). I'll try to dig up a 
specific example.

> I propose that we annotateImplicit() be called from getAnnotatedType() 
> only and maybe directSupertypes() but nothing else.

This seems like it should be okay, but if it breaks tests in a serious 
way we should probably hold off until after the stable release (today).

- Matt