efl_ui : refactoring efl.part in item based classes.
Most of item-based class will have similar efl.part such as text, icon, end.
creating this efl part per each class will be very hard to maintaining the class
and unnecessary eo generation.
so combine them in efl.parts of efl_ui_item.
sub item classes can use this efl.part by declairing ther own eo definition.
Reviewers: cedric, Jaehyun_Cho, segfaultxavi, eagleeye
Reviewed By: cedric, eagleeye
Differential Revision: https://phab.enlightenment.org/D8582