Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
Sometimes services can fail. Failed services will generally not be
restarted by systemd. To start previously failed services we can
just reset their failed state before starting our session target.
GNOME and Plasma do the same thing.
See: https://github.com/alebastr/sway-systemd/pull/11
