efl_ui_widget: unify tree number settings code
the internals of those two methods have been the same. Both setted the
internal numeric flag as either as 1 more or equal to the flag in the
parent object (depending on the internal state). Further details can be
found in the comment in code.
Depends on D11554
Reviewed By: zmike
Differential Revision: https://phab.enlightenment.org/D11555