more resilient subsystems (#1908)

* backing: extract log target

* bitfield-signing: extract log target

* utils: fix a typo

* provisioner: extract log target

* candidate selection: remove unused error variant

* bitfield-distribution: change the return type of run

* pov-distribution: extract log target

* collator-protocol: simplify runtime request

* collation-generation: do not exit early on error

* collation-generation: do not exit on double init

* collator-protocol: do not exit on errors and rename LOG_TARGET

* collator-protocol: a workaround for ununused imports warning

* Update node/network/bitfield-distribution/src/lib.rs

* collation-generation: elevate warn! to error!

* collator-protocol: fix imports

* post merge fix

* fix compilation

polkadot/node/subsystem-util/src/lib.rs

@@ -588,7 +588,7 @@ impl<Spawner: SpawnNamed, Job: 'static + JobTrait> Jobs<Spawner, Job> {
 				if let Some(mut err_tx) = err_tx {
 					// if we can't send the notification of error on the error channel, then
 					// there's no point trying to propagate this error onto the channel too
-					// all we can do is warn that error propagatio has failed
+					// all we can do is warn that error propagation has failed
 					if let Err(e) = err_tx.send((Some(parent_hash), JobsError::Job(e))).await {
 						log::warn!("failed to forward error: {:?}", e);
 					}