The timex collector (enabled by default) needs the
adjtimex syscall, which was disabled by
9fea6d4c85.
So allow it unless the timex collector is disabled.
The systemd collector needs AF_UNIX to talk to
/var/run/dbus/system_bus_socket, which was broken
with 9fea6d4c85.
This commit allows AF_UNIX when needed.
- prometheus exporters are now configured with
`services.prometheus.exporters.<name>`
- the exporters are now defined by attribute sets
from which the options for each exporter are generated
- most of the exporter definitions are used unchanged,
except for some changes that should't have any impact
on the functionality.
