Track circuit related metrics (relay side) on network health relays

I guess it does not make much sense to start tracking the metrics implemented in tpo/core/tor#40816 (closed) in our metrics infrastructure as we do in the metrics/monitoring-and-alerting project. Rather, I think we want to get them set up on our network health relays. Once this is done (which this ticket is for) we can define alert thresholds for those metrics either in tpo/tpa/prometheus-alerts#9 or some follow-up ticket.