eo: remove class functions from eo

eo: remove class functions from eo

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
dropped.

This fixes T7675.

Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D7902