Update the full node networking service to latest good practices (#1437)

* Remove `process_network_service_events`

* Introduce `WakeUpReason`

* Add `WakeUpReason::EventSendersReady`

* Move network events handling to WakeUpReason system

* Add `WakeUpReason::MessageToConnection`

* Add `WakeUpReason::CanStartConnect`

* Add `WakeUpReason::CanOpenGossip`

* Add `WakeUpReason::CanAssignSlot`

* Clean up disconnect event

* Log when starting to connect

* Wake up if an event is ready

* Log chain names on no address

* Remove the discovery start task

* Use a separate channel from tasks messages

* Remove incoming connections tasks

* Make shutdown more straight forward

* Print reason for slot unassignment