Expose build metrics

[trey-ivy]

aside from providing a base level of functionality for exploring build metrics via the UI, we should expose build metrics to a time series database like prometheus so that users can roll their own dashboards.

[trey-ivy]

so i did a little research on this and it seems like you can configure grafana to pull from a graphql api pretty easily https://grafana.com/grafana/plugins/retrodaredevil-wildgraphql-datasource/ , so the quickest and most extensible way to implement this would be graphql queries that will let us expose the data we need. we should come up with a series of questions we want to answer about builds and write queries that will help us answer those question. first things that come to mind are things like,
builds

• duration
• users
  targets and tests
• pass
• fail
• durations
• cache hits