Add ratio of connections held by worker in pgbouncer dashboard

This helps to determine the culprit of which worker is dominating the pgbouncer pool, which usually causes backlog of jobs

The query would look something like this: https://dashboards.gitlab.net/explore?schemaVersion=1&panes=%7B%22dx7%22:%7B%22datasource%22:%22e58c2f51-20f8-4f4b-ad48-2968782ca7d6%22,%22queries%22:%5B%7B%22refId%22:%22B%22,%22expr%22:%22sum%28pg_stat_activity_marginalia_sampler_active_count%7Benv%3D%27gprd%27,%20type%3D%5C%22patroni%5C%22,%20application%3D%27sidekiq%27,%20state%21%3D%5C%22idle%5C%22%7D%20and%20on%20%28instance%29%20pg_replication_is_replica%20%3D%3D%200%29%20by%20%28endpoint%29%5Cn%2F%5Cnon%28%29%20group_left%28%29%5Cnsum%28pg_stat_activity_marginalia_sampler_active_count%7Benv%3D%27gprd%27,%20type%3D%5C%22patroni%5C%22,%20application%3D%27sidekiq%27,%20state%21%3D%5C%22idle%5C%22%7D%20and%20on%20%28instance%29%20pg_replication_is_replica%20%3D%3D%200%29%5Cn%22,%22range%22:true,%22instant%22:true,%22datasource%22:%7B%22type%22:%22prometheus%22,%22uid%22:%22e58c2f51-20f8-4f4b-ad48-2968782ca7d6%22%7D,%22editorMode%22:%22code%22,%22legendFormat%22:%22__auto%22,%22interval%22:%22%22%7D%5D,%22range%22:%7B%22from%22:%22now-24h%22,%22to%22:%22now%22%7D%7D%7D&orgId=1

This ticket was created from INC-3386 and was automatically exported by incident.io 🔥