eina: remove eina_promise_data_get has it lead to risky use.
It seems that use of eina_promise_data_get lead to mostly missuse. As it
duplicate other infrastructure which do not have the same problem. So better
remove it and if we need it back, we can just revert this patch later.
Reviewed-by: Mike Blumenkrantz <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D7578