Add set_accomodate_exclusive_zones

Right now a layer shell surface can be set to not be moved and resized by the areas reserved by exclusive zones owned by otther surfaces by setting a magic value of -1 to the exclusive_zone property.

Besides not being a clear API, this has the limitation of allowing a layershell surface to not be moved only if it does not have any exclusive zone by itself, which is ok for "desktop" windows but not for panels.

On a shell where we have all the panels in the same process we know their layout and things are much more controllable if is the client side which asks the panels to be sized correctly

It also becomes possible for more panels to be on the same side, for instance one aligned to the left and one aligned to the right, thing that we do support in Plasma on X11