As in the previous commit explained, we want to get rid of class
functions in eo, and make them just c functions right away.
This commit removes the class parameter from the eo_class_function_set
call, and adjusts the tests to not depend on class functions anymore.
Class functions are now not tested anymore, tests that used them as a
way to test *things* are adjusted to test them now with object
functions, tests that just tested the working of class functions are
This fixes T7675.
Depends on D7901