v-m: Scrape PostgreSQL exporter

The [postgres exporter][0] exposes metrics about the operation and
performance of a PostgreSQL server.  It's currently deployed on
_db0.pyrocufflink.blue_, the primary server of the main PostgreSQL
cluster.

[0]: https://github.com/prometheus-community/postgres_exporter

victoria-metrics/scrape.yml

@@ -444,3 +444,14 @@ scrape_configs:
   - source_labels:
     - __meta_kubernetes_pod_name
     target_label: instance
+
+- job_name: postgresql
+  static_configs:
+  - targets:
+    - db0.pyrocufflink.blue
+  relabel_configs:
+  - source_labels: [__address__]
+    target_label: instance
+  - source_labels: [__address__]
+    target_label: __address__
+    replacement: '$1:9187'