Way for Hyper-Chain Adminstrators to Monitor their Mempool

**Is your feature request related to a problem? Please describe.**
At Hiro, we are discussing various ways to improve our visibility into the mempool at the `stacks-node` level.

What kind of tools are we giving hyper-chain operators to look into their mempool?

Or, for that matter, what is their set-up going to be for monitoring Prometheus metrics?

**Describe the solution you'd like**
This is just an idea for discussion, in case it wasn't on the radar.