Ensure we spawn the block import worker as an essential task (#8155)

* Ensure we spawn the block import worker as an essential task

This pr ensures that we spawn the block import worker as an essential
task. This is quite important as we need to bring down the node when the
block import is done. Besides that it adds some debug output to the
block import worker.

* Don't be stupid :D

substrate/client/service/src/task_manager/mod.rs

@@ -150,6 +150,7 @@ impl sp_core::traits::SpawnNamed for SpawnTaskHandle {
 /// task spawned through it fails. The service should be on the receiver side
 /// and will shut itself down whenever it receives any message, i.e. an
 /// essential task has failed.
+#[derive(Clone)]
 pub struct SpawnEssentialTaskHandle {
 	essential_failed_tx: TracingUnboundedSender<()>,
 	inner: SpawnTaskHandle,
@@ -203,6 +204,16 @@ impl SpawnEssentialTaskHandle {
 	}
 }
 
+impl sp_core::traits::SpawnEssentialNamed for SpawnEssentialTaskHandle {
+	fn spawn_essential_blocking(&self, name: &'static str, future: BoxFuture<'static, ()>) {
+		self.spawn_blocking(name, future);
+	}
+
+	fn spawn_essential(&self, name: &'static str, future: BoxFuture<'static, ()>) {
+		self.spawn(name, future);
+	}
+}
+
 /// Helper struct to manage background/async tasks in Service.
 pub struct TaskManager {
 	/// A future that resolves when the service has exited, this is useful to