sway: refactor with a wrapper
This moves the wrapper functionality from the NixOS module to a new package
(wrapper) that wraps the original sway package (sway-unwrapped). Therefore it's
now also possible to properly use Sway on non-NixOS systems out of the box.
The new submodule for the wrapperFeatures makes it easy to extend the
functionality which should become useful in the future.
This also introduces a GTK wrapper feature to fix issues with icon/GTK themes,
e.g. when running waybar or wofi. This should also work for #67704. If not, we
might have to add some additional dependencies/arguments for this case.