elementary: reduce event generation during object creation by Efl.Ui.WidgetFactory.
We can not freeze the canvas in all scenario as we are sometime building widget fully
asynchronously which prevent holding events on the canvas. Still it is better to do it
for the case we can.
Reviewed-by: SangHyeon Jade Lee <email@example.com>
Reviewed-by: Marcel Hollerbach <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D10685