ecore_wl2: Replace window ids with pointers
There's no benefit to generating ids instead of just using the
Ecore_Wl2_Window pointer in events.
This has the added benefit of working around a really nasty hash collision
bug when multiple ecore_evas engines are used at once.
Depends on D6521
Reviewed By: devilhorns
Subscribers: cedric, committers, zmike
Differential Revision: https://phab.enlightenment.org/D6522