(filter) move ipv6 interface rules, loopback, fw output rules, and fix antispool order (wasn't on top)

rc: fix an infinite loop on tty close

if the tty is closed while the script is running,
it would previously go in an infinite loop trying
to read from and write to the now-defunct tty.

fixes: https://github.com/opnsense/core/issues/1240

(filter) use plain interface mapping in stead of legacy filter_generate_optcfg_array(), there's quite some magic in there which we want to cleanup eventually

PR: https://github.com/opnsense/core/issues/1077

Content follows, for now just use the sweet template Framework
to get this party started.

We're using "motd.in" so allow replacement during package builds.

Since we have pluggable anchors, this is ready to move to
plugins to shink down the base system a bit.

Te idea is simple, start parsing rules in a uniform way, so we're eventually able to display and alter all auto generated rules.
Because of the large set of legacy code rules, we're going to migrate step by step, leaving the current setup intact.