Move alerts into a Grafana dashboard

[anjackson]

Having to check alertmanager seperately is a bit of a pain. Recent versions of Grafan include an AlertManager data source module, which could be use to integrate alert inspection and management into a Grafana dashboard. The module is in alpha but when it's ready, we should take advantage of this and make a new status dashboard that includes it.

Note also that there's a new Prometheus implementation that might be worth checking out: https://cortexmetrics.io/