Network bridge refactoring impl (#1537)

* update networking types

* port over overseer-protocol message types

* Add the collation protocol to network bridge

* message sending

* stub for ConnectToValidators

* add some helper traits and methods to protocol types

* add collator protocol message

* leaves-updating

* peer connection and disconnection

* add utilities for dispatching multiple events

* implement message handling

* add an observedrole enum with equality and no sentry nodes

* derive partial-eq on network bridge event

* add PartialEq impls for network message types

* add Into implementation for observedrole

* port over existing network bridge tests

* add some more tests

* port bitfield distribution

* port over bitfield distribution tests

* add codec indices

* port PoV distribution

* port over PoV distribution tests

* port over statement distribution

* port over statement distribution tests

* update overseer and service-new

* address review comments

* port availability distribution

* port over availability distribution tests