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.
Depends on D7704