r/vmalert: Deploy vmalert

`vmalert` is a component of Victoria Metrics. It handles alerting and
recording rules, periodically executing queries and dispatching alerts
or writing aggregated data back to the TSDB.

roles/vmalert/templates/vmalert.sysconfig.j2

@@ -0,0 +1,12 @@
+{% if vmalert_datasource_url|d %}
+datasource_url={{ vmalert_datasource_url }}
+{% endif %}
+{% if vmalert_notifier_url|d %}
+notifier_url={{ vmalert_notifier_url }}
+{% endif %}
+{% if vmalert_remote_read_url|d %}
+remoteRead_url={{ vmalert_remote_read_url }}
+{% endif %}
+{% if vmalert_remote_write_url|d %}
+remoteWrite_url={{ vmalert_remote_write_url }}
+{% endif %}