Move spawning tasks from thread pools to Service's TaskManager for block importing (#5647)

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

substrate/client/consensus/manual-seal/src/lib.rs

@@ -17,7 +17,7 @@
 //! A manual sealing engine: the engine listens for rpc calls to seal blocks and create forks.
 //! This is suitable for a testing environment.
 
-use futures::prelude::*;
+use futures::{prelude::*, future::BoxFuture};
 use sp_consensus::{
 	Environment, Proposer, ForkChoiceStrategy, BlockImportParams, BlockOrigin, SelectChain,
 	import_queue::{BasicQueue, CacheKeyId, Verifier, BoxBlockImport},
@@ -67,7 +67,8 @@ impl<B: BlockT> Verifier<B> for ManualSealVerifier {
 
 /// Instantiate the import queue for the manual seal consensus engine.
 pub fn import_queue<Block, B>(
-	block_import: BoxBlockImport<Block, TransactionFor<B, Block>>
+	block_import: BoxBlockImport<Block, TransactionFor<B, Block>>,
+	spawner: impl Fn(BoxFuture<'static, ()>) -> ()
 ) -> BasicQueue<Block, TransactionFor<B, Block>>
 	where
 		Block: BlockT,
@@ -78,6 +79,7 @@ pub fn import_queue<Block, B>(
 		Box::new(block_import),
 		None,
 		None,
+		spawner,
 	)
 }