Snapshot sync part 2 (#2098)

* Split block downloader into a module

* Snapshot sync progress

* Warp sync CLI option

* Increased snapshot chunk and ping timeouts

* Fixed an issue with delayed writes

* Updated bootnodes

* Don't run pending IO tasks on shutdown

* Optional first_block; removed insert_snapshot_block

* Fixing expect calls

* Fixed stalled sync

* style and docs

* Update block_sync.rs

[ci:skip]

rpc/src/v1/impls/eth.rs

@@ -257,7 +257,7 @@ impl<C, S: ?Sized, M, EM> Eth for EthClient<C, S, M, EM> where
 		let status = take_weak!(self.sync).status();
 		match status.state {
 			SyncState::Idle => Ok(SyncStatus::None),
-			SyncState::Waiting | SyncState::Blocks | SyncState::NewBlocks | SyncState::ChainHead
+			SyncState::Waiting | SyncState::Blocks | SyncState::NewBlocks
 				| SyncState::SnapshotManifest | SyncState::SnapshotData | SyncState::SnapshotWaiting => {
 				let current_block = U256::from(take_weak!(self.client).chain_info().best_block_number);
 				let highest_block = U256::from(status.highest_block_number.unwrap_or(status.start_block_number));

rpc/src/v1/tests/helpers/sync_provider.rs

@@ -51,6 +51,7 @@ impl TestSyncProvider {
 				mem_used: 0,
 				num_snapshot_chunks: 0,
 				snapshot_chunks_done: 0,
+				last_imported_old_block_number: None,
 			}),
 		}
 	}