update peer scoring to prevent us from going over max peers, update network ConnManager `Connected` not to handle that

[noot]

Task summary

• currently in the ConnManager.Connected() function, which is called when a new connection is opened, it checks whether we are over our max peers, and if so randomly disconnects from a peer
• this should be handled by the peer scoring module instead (so the lowest scored peer is removed), but if Connected() is updated not to perform that functionality, we go over our max peer count (by a significant amount), can be seen by running a polkadot or kusama node