BREAKING CHANGE: gtk-layer-shell is now required and unconditionally
used. The corresponding config option is removed.
As a part of preparation for future versions of GTK, remove an ability
to use wlr-layer-shell directly. The APIs it required were dropped in
GTK4, and with the menus/tooltips positioning issue being practically
unsolvable it doesn't make sense to keep maintaining the code.
d6d164a27d