BridgeHub[Rococo/Wococo] test batched relaying of messages and their dispatch (#2578)

Added some tests that aim to cover the runtime configuration
that is exercised when BH receives relayed complex message.

* checks correct importing of proofs for:
  bridged chain finality, bridged para heads, bridged messages,
* checks relayer extension correctly configured to reward
  submitting relayer,
* checks relayed message is successfully dispatched.

Also moved generic test-utils from
  `asset-test-utils: parachains/runtimes/assets/test-utils`
one level up to new crate
  `parachains-runtimes-test-utils: parachains/runtimes/test-utils`
to be reused by BridgeHubs.

Signed-off-by: acatangiu <adrian@parity.io>
Co-authored-by: Branislav Kontur <bkontur@gmail.com>

cumulus/parachains/runtimes/bridge-hubs/test-utils/src/lib.rs

@@ -1,4 +1,4 @@
-// Copyright 2023 Parity Technologies (UK) Ltd.
+// Copyright Parity Technologies (UK) Ltd.
 // This file is part of Cumulus.
 
 // Cumulus is free software: you can redistribute it and/or modify
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
 
-pub use bp_test_utils::test_header;
+//! Module contains predefined test-case scenarios for "BridgeHub" `Runtime`s.
+
 pub mod test_cases;
-pub use test_cases::CollatorSessionKeys;
+pub use bp_test_utils::test_header;
+pub use parachains_runtimes_test_utils::*;