[FR]: Add monitoring of evidence size and task success status

[aarontp]

What is the feature you are proposing?

Add monitoring metrics for evidence size and task success status (e.g. evidence size for both successful and failed tasks) to be graphed in Grafana.

What would this feature improve or what problem would it solve?

This is to track how failures correlate with evidence size and the overall evidence size over time.

What alternatives have you considered?

No response