Parachain improvements (#1905)

* Parachain improvements

- Set the parachains configuration in Rococo genesis
- Don't stop the overseer when a subsystem job is stopped
- Several small code changes

* Remove unused functionality

* Return error from the runtime instead of printing it

* Apply suggestions from code review

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Update primitives/src/v1.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Update primitives/src/v1.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Fix test

* Revert "Update primitives/src/v1.rs"

This reverts commit 11fce2785acd1de481ca57815b8e18400f09fd52.

* Revert "Update primitives/src/v1.rs"

This reverts commit d6439fed4f954360c89fb1e12b73954902c76a41.

* Revert "Return error from the runtime instead of printing it"

This reverts commit cb4b5c0830ac516a6d54b2c24197e9354f2b98cb.

* Revert "Fix test"

This reverts commit 0c5fa1b5566d4cd3c55a55d485e707165ce7a59e.

* Update runtime/parachains/src/runtime_api_impl/v1.rs

Co-authored-by: Sergei Shulepov <sergei@parity.io>

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
Co-authored-by: Sergei Shulepov <sergei@parity.io>

polkadot/node/core/backing/src/lib.rs

@@ -288,7 +288,7 @@ impl CandidateBackingJob {
 				ToJob::CandidateBacking(msg) => {
 					self.process_msg(msg).await?;
 				}
-				_ => break,
+				ToJob::Stop => break,
 			}
 		}
 
@@ -838,7 +838,7 @@ impl util::JobTrait for CandidateBackingJob {
 
 			let (assignment, required_collator) = match assignment {
 				None => return Ok(()), // no need to work.
-				Some((a, r)) => (a, r),
+				Some(r) => r,
 			};
 
 			let job = CandidateBackingJob {