elementary: refactor selection manager to not use eina_promise_data_set.
eina_promise_data_set is a misleading API and result in conflicted use by
multiple independent piece of code leading to bug and crash. It is also not
necessary and we can avoid using it completely.
Reviewed-by: Mike Blumenkrantz <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D7543