Extract syncing protocol from sc-network (#12828)

* Move import queue out of `sc-network`

Add supplementary asynchronous API for the import queue which means
it can be run as an independent task and communicated with through
the `ImportQueueService`.

This commit removes removes block and justification imports from
`sc-network` and provides `ChainSync` with a handle to import queue so
it can import blocks and justifications. Polling of the import queue is
moved complete out of `sc-network` and `sc_consensus::Link` is
implemented for `ChainSyncInterfaceHandled` so the import queue
can still influence the syncing process.

* Move stuff to SyncingEngine

* Move `ChainSync` instanation to `SyncingEngine`

Some of the tests have to be rewritten

* Move peer hashmap to `SyncingEngine`

* Let `SyncingEngine` to implement `ChainSyncInterface`

* Introduce `SyncStatusProvider`

* Move `sync_peer_(connected|disconnected)` to `SyncingEngine`

* Implement `SyncEventStream`

Remove `SyncConnected`/`SyncDisconnected` events from
`NetworkEvenStream` and provide those events through
`ChainSyncInterface` instead.

Modify BEEFY/GRANDPA/transactions protocol and `NetworkGossip` to take
`SyncEventStream` object which they listen to for incoming sync peer
events.

* Introduce `ChainSyncInterface`

This interface provides a set of miscellaneous functions that other
subsystems can use to query, for example, the syncing status.

* Move event stream polling to `SyncingEngine`

Subscribe to `NetworkStreamEvent` and poll the incoming notifications
and substream events from `SyncingEngine`.

The code needs refactoring.

* Make `SyncingEngine` into an asynchronous runner

This commits removes the last hard dependency of syncing from
`sc-network` meaning the protocol now lives completely outside of
`sc-network`, ignoring the hardcoded peerset entry which will be
addressed in the future.

Code needs a lot of refactoring.

* Fix warnings

* Code refactoring

* Use `SyncingService` for BEEFY

* Use `SyncingService` for GRANDPA

* Remove call delegation from `NetworkService`

* Remove `ChainSyncService`

* Remove `ChainSync` service tests

They were written for the sole purpose of verifying that `NetworWorker`
continues to function while the calls are being dispatched to
`ChainSync`.

* Refactor code

* Refactor code

* Update client/finality-grandpa/src/communication/tests.rs

Co-authored-by: Anton <anton.kalyaev@gmail.com>

* Fix warnings

* Apply review comments

* Fix docs

* Fix test

* cargo-fmt

* Update client/network/sync/src/engine.rs

Co-authored-by: Anton <anton.kalyaev@gmail.com>

* Update client/network/sync/src/engine.rs

Co-authored-by: Anton <anton.kalyaev@gmail.com>

* Add missing docs

* Refactor code

---------

Co-authored-by: Anton <anton.kalyaev@gmail.com>

substrate/client/informant/src/display.rs

@@ -24,7 +24,7 @@ use sc_network_common::{
 	service::NetworkStatus,
 	sync::{
 		warp::{WarpSyncPhase, WarpSyncProgress},
-		SyncState,
+		SyncState, SyncStatus,
 	},
 };
 use sp_runtime::traits::{Block as BlockT, CheckedDiv, NumberFor, Saturating, Zero};
@@ -69,7 +69,12 @@ impl<B: BlockT> InformantDisplay<B> {
 	}
 
 	/// Displays the informant by calling `info!`.
-	pub fn display(&mut self, info: &ClientInfo<B>, net_status: NetworkStatus<B>) {
+	pub fn display(
+		&mut self,
+		info: &ClientInfo<B>,
+		net_status: NetworkStatus,
+		sync_status: SyncStatus<B>,
+	) {
 		let best_number = info.chain.best_number;
 		let best_hash = info.chain.best_hash;
 		let finalized_number = info.chain.finalized_number;
@@ -94,7 +99,7 @@ impl<B: BlockT> InformantDisplay<B> {
 		};
 
 		let (level, status, target) =
-			match (net_status.sync_state, net_status.state_sync, net_status.warp_sync) {
+			match (sync_status.state, sync_status.state_sync, sync_status.warp_sync) {
 				(
 					_,
 					_,