Consolidate BIND DNS into one bind-internal namespace

Reshapes the three DNS tiers from separate ns-* namespaces into a single
bind-internal namespace and renames the StatefulSets, and scopes the TSIG
keys to their cluster (needs the clusterRef field from operator v0.1.3).

- move the 3 clusters + zones + keys into apps/base/bind-internal:
  BindCluster names bind-authoritative / bind-resolvers / bind-externaldns
  (= StatefulSet names), LBs kept on .6/.7/.8, external-dns hostnames renamed
- add clusterRef to the transfer-key (bind-authoritative) and externaldns-key
  (bind-externaldns) TSIG keys so they no longer leak across clusters
- remove the old ns-auth / ns-resolver / ns-externaldns apps
- ApplicationSet + AppProject: replace the three ns-* entries with bind-internal
- bump bind-system operator to v0.1.3 (CRD install link + image) so the CRDs
  understand the new clusterRef field
- operator stays in bind-system (unchanged)

apps/base/bind-internal/externaldns/zones.yaml

@@ -0,0 +1,34 @@
+# k8s external-dns zones migrated from puppet-prod
+# (externaldns::k8s_zones in hieradata/roles/infra/dns/externaldns.yaml).
+# Primary + dynamicUpdate: the Kubernetes external-dns controller writes
+# records here via RFC2136 authenticated with externaldns-key.
+---
+apiVersion: bind.unkin.net/v1alpha1
+kind: BindZone
+metadata:
+  name: k8s-syd1-au-unkin-net
+  namespace: bind-internal
+spec:
+  clusterRef: bind-externaldns
+  zoneName: k8s.syd1.au.unkin.net
+  type: primary
+  defaultTTL: 600
+  dynamicUpdate: true
+  updateKeyRef: externaldns-key
+  allowTransfer:
+    - key externaldns-key
+---
+apiVersion: bind.unkin.net/v1alpha1
+kind: BindZone
+metadata:
+  name: 200-18-198-in-addr-arpa
+  namespace: bind-internal
+spec:
+  clusterRef: bind-externaldns
+  zoneName: 200.18.198.in-addr.arpa
+  type: primary
+  defaultTTL: 600
+  dynamicUpdate: true
+  updateKeyRef: externaldns-key
+  allowTransfer:
+    - key externaldns-key