The existing units were never used as the corresponding support was
never merged into gnome-session.
This commits updates units to be usable with the newer gnome-session
unit definitions. Also added is appropriate failure/restart logic
including the ability to disable extensions. Note that extensions will
only be disabled if a failure happens in the first two minutes after
login.
https://gitlab.gnome.org/GNOME/gnome-session/merge_requests/13https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/507
