csharp: Fix wrapping of private classes
Summary:
Sometimes, valid Eo objects of private classes can be returned from
methods. Currently we try to wrap in a minimal `Efl.Object` instance,
but as it is an abstract class, we can't instantiate directly.
This commits adds a dummy `Efl.ObjectRealized` to be instantiated when
wrapping such classes alongside a test case.
Fixes: T8258
Reviewers: felipealmeida, brunobelo, segfaultxavi, Jaehyun_Cho
Reviewed By: brunobelo
Subscribers: cedric, #reviewers, #committers
Tags: #efl
Differential Revision: https://phab.enlightenment.org/D10101