Investigate using Consul to find Prometheus for Topology Ping

In order for the topology usage ping to work in a multi-node setup, we need to know where Prometheus is listening. One avenue we had identified in #30175 (closed) is to add a new settings key that would carry that address. However, this requires user interaction, so it might not be a reliable source, since by the time we would launch it, no one would be using this yet.

Since we recommend running Consul for service discovery in multi-node setups, we could instead just ask Consul for where Prometheus can be reached. For example, for gitlab.com, discovering Prometheus can be done by querying Consul DNS (localhost@8600) for prometheus.service.consul (an SRV record.) See &3576 (comment 361180501)

Consul can also be queried for the services it manages via http://localhost:8500/v1/catalog/services.