Create a grafana dashboard for YugabyteDB

[iSignal]

We've had a few requests for a pre existing grafana dashboard that can be customized.

https://blog.yugabyte.com/monitoring-yugabytedb-with-prometheus-and-grafana-in-kubernetes/ has some initial info to get started.

For the specific metrics that would be good to have in a dashboard, https://github.com/yugabyte/yugabyte-db/blob/master/managed/src/main/resources/metrics.yml is a good collection to use.

https://grafana.com/grafana/dashboards could be one location to put this dashboard up at. We could also check it into one of our repos.

[iSignal]

https://grafana.com/grafana/dashboards/12528 is the Grafana community dashboard that corresponds to the Grafana JSON spec at https://github.com/yugabyte/yugabyte-db/blob/master/cloud/grafana/YugabyteDB.json.