refactor(configuration): centralize DNS list variables in network dispatch

roles/configuration/templates/network.j2

@@ -9,8 +9,8 @@ interface-name={{ configuration_iface_name }}
 
 [ipv4]
 {% set iface = configuration_iface %}
-{% set dns_list = system_cfg.network.dns.servers | default([]) %}
-{% set search_list = system_cfg.network.dns.search | default([]) %}
+{% set dns_list = configuration_dns_list %}
+{% set search_list = configuration_dns_search %}
 {% if iface.ip | default('') | string | length %}
 address1={{ iface.ip }}/{{ iface.prefix }}{{ (',' ~ iface.gateway) if (iface.gateway | default('') | string | length) else '' }}
 method=manual