(PUP-2833) Make all types inherit PAnyType

Some types inherited PAbstractType (to indicate they where not
concrete). This just causes confusion when using the Ruby API
to check if a Type is PAnyType.

This makes all types inherit from PAnyType (which is the only
type inheriting from PAbstractType).
Merge pull request #2803 from hlindberg/PUP-2833_all-types-are-any

(PUP-2833) Make all types inherit PAnyType