Remote-display windows for CES IC demo

Under the legacy WindowManager, the CES demo picks a hard-coded range of surface IDs to be placed on the remote display, to forward the IC content to the correct screen.

We need a similar solution with the new WM which will allow us to do the same. Probably the best option is to add a per-output list of XDG app IDs whose views should always be placed on that display, so it can be reconfigured without recompilation.

cc scottm