r/v-m: Add role for Victoria Metrics

The *victoria-metrics* role deploys a single-server instance of the
Victoria Metrics time series database server.  It installs the selected
version by downloading the binary release from Github and copying it to
`/usr/local/sbin` on the managed node.  Scrape configuration is optional
and can be specified with the `scrape_configs` variable.

roles/victoria-metrics/defaults/main.yml

@@ -0,0 +1,13 @@
+vm_version: 1.72.0
+
+vm_retention_period: 12
+vm_self_scrape: true
+vm_self_scrape_interval: '{{ vm_default_scrape_interval|d("1m") }}'
+
+vm_scrape_configs: []
+
+vm_config:
+  global:
+    scrape_interval: 1m
+
+  scrape_configs: "{{ vm_scrape_configs }}"