A toolbox created by the script can be used as the base of a pet
container that is manually updated with new dependencies over time
and accumalates additional packages; or it can be used as a deposable
container that is recreated each time the dependencies change.
To make the latter case more convenient, add a --replace option
that deletes an existing toolbox before creating the new one.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2713>
The script is a thin wrapper around `toolbox create`, mainly to
avoid the tedious image names. In addition, it allows us to
ensure that the container includes a matching mutter version.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2713>