feat: setup metrics agents

- set puppet::puppetdb_api class to export puppetdb
- set infra::dns::server class to export bind
- set all to export node and systemd metrics

site/profiles/manifests/metrics/default.pp

@@ -0,0 +1,11 @@
+# profiles::metrics::default
+#
+# these exporters will be setup on all nodes
+class profiles::metrics::default (
+  Boolean $node_exporter      = true,
+  Boolean $systemd_exporter   = true,
+) {
+
+  include prometheus::node_exporter
+  include prometheus::systemd_exporter
+}