Rewrite the BasiQueue using channels (#1327)

* use channels to implement basic import queue

* async justification import

* better conditional for is_done in tests

* reword the test for presence of link

* fix conditional

* trace instead of panic when no link present

* reword expectations when sending to importers

* fix

* debug justification import error

* update expectations

* use NumberFor

* nits

* add general description

* move error handling into closure

substrate/node/cli/src/service.rs

@@ -120,12 +120,8 @@ construct_service_factory! {
 		},
 		LightService = LightComponents<Self>
 			{ |config, executor| <LightComponents<Factory>>::new(config, executor) },
-		FullImportQueue = AuraImportQueue<
-			Self::Block,
-			FullClient<Self>,
-			NothingExtra,
-		>
-			{ |config: &mut FactoryFullConfiguration<Self>, client: Arc<FullClient<Self>>| {
+		FullImportQueue = AuraImportQueue<Self::Block>
+			{ |config: &mut FactoryFullConfiguration<Self> , client: Arc<FullClient<Self>>| {
 				let slot_duration = SlotDuration::get_or_compute(&*client)?;
 				let (block_import, link_half) =
 					grandpa::block_import::<_, _, _, RuntimeApi, FullClient<Self>>(
@@ -145,11 +141,7 @@ construct_service_factory! {
 					config.custom.inherent_data_providers.clone(),
 				).map_err(Into::into)
 			}},
-		LightImportQueue = AuraImportQueue<
-			Self::Block,
-			LightClient<Self>,
-			NothingExtra,
-		>
+		LightImportQueue = AuraImportQueue<Self::Block>
 			{ |config: &FactoryFullConfiguration<Self>, client: Arc<LightClient<Self>>| {
 					import_queue(
 						SlotDuration::get_or_compute(&*client)?,