Migrates the two zones the puppet external-dns instances serve
(externaldns::k8s_zones) as dynamic BindZone CRs on the externaldns
cluster, plus a catalog zone so they replicate to the secondaries.
- add apps/base/ns-externaldns/zones.yaml: k8s.syd1.au.unkin.net and
200.18.198.in-addr.arpa (primary, dynamicUpdate via externaldns-key)
- add a BindCatalogZone so external-dns writes to the primary replicate
unkinben