efl_ui_item: use signals from the theme and not object
the problem here is that when we are using the signals from the object,
then the edje object itself will receive press/unpress events before
any content that is swallowed into the edje object.
This means, that no clickable content, added to a item could be clicked
without selecting / unselecting the item. Which was a problem.
With this commit the theme is sending signals which are then passed to
the efl.input.clickable mixin, this way, the part is stacked below the
added content, which means, clickable content will not select / unselect
the item anymore.
Reviewed-by: Cedric BAIL <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D10892