fix(comms): only reap when number of connections exceeds threshold

[sdbondi]

Description

• only release connection handles of non-neighbouring peers after successful connect
• adds min threshold for connection reaping with default 50
• only reap connections that have less than 3 substreams
• only reap "excess" (num_connections - 50) connections
• adds RpcServer query that returns number of sessions for a peer
• updates list-connections command to display number of peer connection handles and rpc sessions
• updates list-connections to display two tables, one with wallets and one with base nodes

Motivation and Context

Previously, connection handles would be dropped (making them reapable) when refreshing the neighbour peer pool. The neighbour pool only starts the attempt to connect, but the non-neighbouring connection handles should only be dropped if a replacement neighbour was actually able to connect.
Reaping should only apply when we have many connections, otherwise many connections are acceptable.

Fixes #4608

How Has This Been Tested?

Manually, checking that connections to other base nodes/wallets running this PR stay connected