[wayland] Simplify output handling

Summary:
Instead of changing lifespan of kwayland objects we can just call
create() and delete() on it which affects the lifespan of the underlying
resource, but not the kwayland wrapper.

This gets rid of some duplicate syncing.

Test Plan:
Ran WAYLAND_DEBUG=1
plugged in and removed a monitor
output showed wl_output and xdg_output being handled correctly

Reviewers: KWin, zzag

Reviewed By: KWin, zzag

Subscribers: zzag, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D27899