When a session is locked, no views are visible and there is no way to
interact with the user session. This means that all inhibitors based on
visibility - with the exception being inhibitors on the session lock
surfaces themselves - become inert, allowing the session to go idle.
The only inhibitor type on normal views that one could argue should
remain active is INHIBIT_IDLE_OPEN, but for now we disable all view
inhibitors regardless of type.
Arranging lock surfaces rely on the sway_output width and height being
updated, but these are only updated after the commit has been completed
and all commit listeners have executed. This means that the lock
surfaces will not be appropriately scaled to match a change in output
dimensions, and may reveal what is under the lock background.
Replace the implicit arrange through the output commit listener with an
explicit arrange after the output configuration is finalized.
This might have regressed by other transition away from output commit
listeners for other arrange tasks, but even then it would have
erroneously relied on signalling order.
When removing outputs, it is possible to end up in a situation where
none of the session lock client's surfaces have keyboard focus,
resulting in it not receiving keyboard events. Track the focused
surface and update it as needed on surface destroy.
