Implement Network Bridge (#1280)

* network bridge skeleton

* move some primitives around and add debug impls

* protocol registration glue & abstract network interface

* add send_msgs to subsystemctx

* select logic

* transform different events into actions and handle

* implement remaining network bridge state machine

* start test skeleton

* make network methods asynchronous

* extract subsystem out to subsystem crate

* port over overseer to subsystem context trait

* fix minimal example

* fix overseer doc test

* update network-bridge crate

* write a subsystem test-helpers crate

* write a network test helper for network-bridge

* set up (broken) view test

* Revamp network to be more async-friendly and not require Sync

* fix spacing

* fix test compilation

* insert side-channel for actions

* Add some more message types to AllMessages

* introduce a test harness

* add some tests

* ensure service compiles and passes tests

* fix typo

* fix service-new compilation

* Subsystem test helpers send messages synchronously

* remove smelly action inspector

* remove superfluous let binding

* fix warnings

* Update node/network/bridge/src/lib.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* fix compilation

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

polkadot/Cargo.toml

@@ -42,10 +42,12 @@ members = [
 	"service",
 	"validation",
 
-	"node/messages",
+	"node/network/bridge",
 	"node/overseer",
 	"node/primitives",
 	"node/service",
+	"node/subsystem",
+	"node/test-helpers/subsystem",
 
 	"parachain/test-parachains",
 	"parachain/test-parachains/adder",