elementary: update Efl.Ui.Caching_Factory to rely on Efl.Ui.Widget_Factory for Efl.Ui.Widget.
I am not sure we really need Efl.Ui.Caching_Factory after this, but in case we want a Caching_Factory
for non Efl.Ui.Widget, this is supported by this patch (And is the reason why most of the complexity).
The benefit from inheriting from Efl.Ui.Widget_Factory allow to get the style of an Efl.Ui.Widget
defined by an Efl.Model properly done at creation time.
Reviewed-by: SangHyeon Jade Lee <email@example.com>
Reviewed-by: Larry Lira <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D7705