tests/edje: add comprehensive edje reloading test

tests/edje: add comprehensive edje reloading test

Summary:
this verifies:
* successfully loading a file
* emission of "load" signal when performing a file load
* swallowing an object
* no-op of file load operation on same file if mtime is unchanged
* successfully reloading the same file if the mtime has changed
* preserving user-defined data across file reloads

Depends on D9877

Reviewers: cedric

Reviewed By: cedric

Subscribers: #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9878