It never gained traction, was only used in thee places, and
the class(-hierarchy) is not really needed and only complicates
the code when the formatter creation is handled in free functions.
Also adapt the users.
Change-Id: Ieef7199f5a36f244b2f38cffef71a5fe0606065c
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>