feat(bind9): support systemd drop-ins

Keep role configuration namespaced and allow hosts to customize systemd startup.

Co-authored-by: Copilot <copilot@github.com>

templates/etc/named/named.conf.views.j2

@@ -148,11 +148,11 @@ view "{{ view.name }}" {
     #   contact the Master, ffor whatever reason, the zone may be left with
     #   no effective Authoritative Name Servers.
 {% if zone.file is defined and zone.file | length > 0 and not zone.file.startswith('/') %}
-    file "{{ bind_config_directory }}/{{ zone.config.file }}";
+    file "{{ bind9_config_directory }}/{{ zone.config.file }}";
 {% elif zone.file is defined and zone.file | length > 0 and zone.file.startswith('/')%}
     file "{{ zone.config.file }}";
 {% else %}
-    # file "{{ bind_config_directory }}/...";
+    # file "{{ bind9_config_directory }}/...";
 {% endif %}
 
     # This option is only meaningful if the forwarders list is not empty. A