This adds a trigger to postmarketos-base-systemd that runs
systemctl preset-all any time unit files are changed on the system.
This means we can drop the systemd macro for pkg pre-install/de-install
scripts, and avoid making abuild complicated for handling systemd stuff.
The downside with this approach is that users who want to permanently
disable can no longer do systemctl disable <unit>, and instead have
to do systemctl mask <unit>. Given how much this improves other stuff,
especially wrt upstreaming the abuild split func stuff, I think this
is a worthwhile trade-off. We can always improve on this more in the
future, since this trigger thing would be easy to rollback/replace.
What about cleaning up links made from systemd preset that are
broken after a pkg providing the enabled unit file was removed?
This could be copied from the systemd macro's pre-deinstall func and
included in the trigger somehow?
