r/vmagent: Deploy vmagent

The *vmagent* role installs and configures the scraping and routing
agent used in the Victoria Metrics ecosystem.

roles/vmagent/defaults/main.yml

@@ -0,0 +1,10 @@
+vmagent_remotewrite_url: http://[::1]:8428/api/v1/write
+
+vmagent_scrape_interval: 1m
+vmagent_scrape_configs: []
+
+vmagent_config:
+  global:
+    scrape_interval: '{{ vmagent_scrape_interval }}'
+
+  scrape_configs: "{{ vmagent_scrape_configs }}"