Import target block body during warp sync (#12300)

* Receive and import target block body

* Request target block

* minor: wording

* Check for block body in the test

* Import target block justifications

* Fix: do not fail block validation if no justifications received

* Fix: import target blocks without justifications

Co-authored-by: arkpar <arkady.paronyan@gmail.com>

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

@@ -96,6 +96,8 @@ pub enum OnBlockData<Block: BlockT> {
 	Import(BlockOrigin, Vec<IncomingBlock<Block>>),
 	/// A new block request needs to be made to the given peer.
 	Request(PeerId, BlockRequest<Block>),
+	/// Continue processing events.
+	Continue,
 }
 
 /// Result of [`ChainSync::on_block_justification`].

substrate/client/network/common/src/sync/warp.rs

@@ -64,6 +64,8 @@ pub enum WarpSyncPhase<Block: BlockT> {
 	AwaitingPeers,
 	/// Downloading and verifying grandpa warp proofs.
 	DownloadingWarpProofs,
+	/// Downloading target block.
+	DownloadingTargetBlock,
 	/// Downloading state data.
 	DownloadingState,
 	/// Importing state.
@@ -77,6 +79,7 @@ impl<Block: BlockT> fmt::Display for WarpSyncPhase<Block> {
 		match self {
 			Self::AwaitingPeers => write!(f, "Waiting for peers"),
 			Self::DownloadingWarpProofs => write!(f, "Downloading finality proofs"),
+			Self::DownloadingTargetBlock => write!(f, "Downloading target block"),
 			Self::DownloadingState => write!(f, "Downloading state"),
 			Self::ImportingState => write!(f, "Importing state"),
 			Self::DownloadingBlocks(n) => write!(f, "Downloading block history (#{})", n),