efl: Make stable single-valued getters consistent.
Summary:
Instead of a getter with an explicit return type, change it to be a
single-valued property.
The eolian C generator takes care of making this single value the actual
return value of the C function.
This also makes these properties able to be reflected on.
The stack properties returns just a pointer and not a new ref, so no
@move needed.
Beta properties will be handled in a future commit.
Depends on D10601
Reviewers: segfaultxavi, bu5hm4n, q66, cedric
Reviewed By: segfaultxavi
Subscribers: #reviewers, #committers, brunobelo, felipealmeida
Tags: #efl
Differential Revision: https://phab.enlightenment.org/D10602