Network sync refactoring (part 4) (#11412)

* Remove direct dependency of `sc-network` on `sc-network-light`

* Move `WarpSyncProvider` trait and surrounding data structures into `sc-network-common`

* Move `WarpSyncProvider` trait and surrounding data structures into `sc-network-common`

* Create `sync` module in `sc-network-common`, create `ChainSync` trait there (not used yet), move a bunch of associated data structures from `sc-network-sync`

* Switch from concrete implementation to `ChainSync` trait from `sc-network-common`

* Introduce `OpaqueStateRequest`/`OpaqueStateResponse` to remove generics from `StateSync` trait

* Introduce `OpaqueBlockRequest`/`OpaqueBlockResponse`, make `scheme` module of `sc-network-sync` private

* Surface `sc-network-sync` into `sc-service` and make `sc-network` not depend on it anymore

* Remove now unnecessary dependency from `sc-network`

* Replace crate links with just text since dependencies are gone now

* Remove `warp_sync` re-export from `sc-network-common`

* Update copyright in network-related files

* Address review comments about documentation

* Apply review suggestion

* Rename `extra_requests` module to `metrics`

Co-authored-by: Bastian Köcher <info@kchr.de>

substrate/client/network/sync/src/block_request_handler.rs

@@ -17,10 +17,7 @@
 //! Helper for handling (i.e. answering) block requests from a remote peer via the
 //! `crate::request_responses::RequestResponsesBehaviour`.
 
-use crate::{
-	message::BlockAttributes,
-	schema::v1::{block_request::FromBlock, BlockResponse, Direction},
-};
+use crate::schema::v1::{block_request::FromBlock, BlockResponse, Direction};
 use codec::{Decode, Encode};
 use futures::{
 	channel::{mpsc, oneshot},
@@ -34,6 +31,7 @@ use sc_client_api::BlockBackend;
 use sc_network_common::{
 	config::ProtocolId,
 	request_responses::{IncomingRequest, OutgoingResponse, ProtocolConfig},
+	sync::message::BlockAttributes,
 };
 use sp_blockchain::HeaderBackend;
 use sp_runtime::{