xwayland: connect commit and surface_destroy handlers together

xwayland: connect commit and surface_destroy handlers together

Factor out set_surface() which consolidates connecting/disconnecting
the wlr_surface event listeners in one place.

In theory, this means we can receive commit events for minimized views.
However, with a test app that resizes itself, I didn't see any change,
i.e. the commits still don't come through until un-minimize. It's
possible they are being filtered at wlroots or protocol level.

Also remove an old, semi-related TODO from view.c.