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/cli/src/arg_enums.rs

@@ -251,15 +251,19 @@ pub enum SyncMode {
 	Warp,
 }
 
-impl Into<sc_network::config::SyncMode> for SyncMode {
-	fn into(self) -> sc_network::config::SyncMode {
+impl Into<sc_network_common::config::SyncMode> for SyncMode {
+	fn into(self) -> sc_network_common::config::SyncMode {
 		match self {
-			SyncMode::Full => sc_network::config::SyncMode::Full,
-			SyncMode::Fast =>
-				sc_network::config::SyncMode::Fast { skip_proofs: false, storage_chain_mode: false },
-			SyncMode::FastUnsafe =>
-				sc_network::config::SyncMode::Fast { skip_proofs: true, storage_chain_mode: false },
-			SyncMode::Warp => sc_network::config::SyncMode::Warp,
+			SyncMode::Full => sc_network_common::config::SyncMode::Full,
+			SyncMode::Fast => sc_network_common::config::SyncMode::Fast {
+				skip_proofs: false,
+				storage_chain_mode: false,
+			},
+			SyncMode::FastUnsafe => sc_network_common::config::SyncMode::Fast {
+				skip_proofs: true,
+				storage_chain_mode: false,
+			},
+			SyncMode::Warp => sc_network_common::config::SyncMode::Warp,
 		}
 	}
 }