Create metrics endpoint for external platform monitoring

[ssplatt]

One industry standard in the Operations world is to have programs expose internal metrics via a /metrics endpoint for monitoring systems like Prometheus to scrape and aggregate the data. This data can then be queried, shipped, graphed, and alerted upon. Potentially, this could result in an alert to the user or system administrator when a Task has died prematurely or similar. At the very least, if could be a part of making a visually appealing dashboard, like Grafana, with a full overview of what the SA system or cluster is doing.

• potentially use the prom-client node module, https://github.com/siimon/prom-client, to aggregate and expose the internal metrics
• general information on Prometheus and it's own internal metrics endpoint as a demonstration https://prometheus.io/docs/prometheus/latest/getting_started/
• example of Fluent Bit implementation of /metrics - https://docs.fluentbit.io/manual/administration/monitoring#metrics-examples