`PeerManager::new_routing_only` incompatible with `lightning-net-tokio`

[jkczyz]

PeerManager::new_routing_only (and PeerManager::new_channel_only) doesn't work with lightning-net-tokio because setup_inbound and setup_outbound take a PeerManager with Arc parameters but the PeerManager::new_routing_only returns a PeerManager without using an Arc for the RoutingMessageHandler.

Reported by a participant at the Bitcoin++ hackathon. Workaround is to instantiated the PeerManager using an Arc for the parameter instead of using PeerManager::new_routing_only.

[TheBlueMatt]

Yuck. We should make the generic parameters in lightning-net-tokio more..generic and let them be Deref + Sync or whatever is needed to make tokio happy.

[wpaulino]

#1623