EPIC: Auto-Manage Connections to Configured Peers

[bhazzard]

As a first step towards P2P discovery, we'll add a feature to automate connection management so that nodes can be configured to use a published list of public peers, and stay connected to a subset of them.

To do this, we'll add a new option to limit the number of configured peers a node should remain connected to, and implement heuristics to define how many block relay, transaction relay, or finalizer vote relay nodes each node should be connected to.