Handle output destruction - handle hotplug of connectors

Close for OO M2

All of the have been merged in master.

While this fixes the compositor crash on un-plugging, re-plugging it back seems to cause a libweston assert, which I don't really see on master/main so that's need a further bisect to see what we might need.

Note that this with libweston 10, and not libweston 9, I'm not sure this really applies to it.

Let me know if anyone needs a backport for libweston 9.