feat(data): replace D-Bus activation service with init script

D-Bus activation without systemd, specially for system daemons has a big set of drawbacks. Including no supervision, no way for the user to configure the arguments sent, and no way to set the environment. In our specific use-case, it already generated an issue[1] where the appstream downloader was not found because the PATH is not part of the DBus activation environment, and there's no possibility to actually fix it. Fix that by instead making apk-polkit-server a supervised system daemon. At the same time, remove the D-Bus service, to make sure that the service is not "by-mistake" activated before the system daemon is.

In pmOS we will automatically enable this service. In alpine, by policy users have to do it themselves, so we'll have to add to the release notes.

[1] alpine/aports!44981 (merged)

@Newbyte, I guess this is the follow-up from[1]. Probably the right way to fix it.