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/bridge-hub-rococo/Cargo.toml

@@ -91,6 +91,7 @@ bridge-runtime-common = { path = "../../../../bridges/bin/runtime-common", defau
 static_assertions = "1.1"
 bridge-hub-test-utils = { path = "../test-utils"}
 bridge-runtime-common = { path = "../../../../bridges/bin/runtime-common", features = ["integrity-test"] }
+sp-keyring = { git = "https://github.com/paritytech/substrate", branch = "master" }
 
 [features]
 default = [
@@ -119,6 +120,7 @@ std = [
 	"cumulus-primitives-core/std",
 	"cumulus-primitives-timestamp/std",
 	"cumulus-primitives-utility/std",
+	"frame-benchmarking/std",
 	"frame-executive/std",
 	"frame-support/std",
 	"frame-system-rpc-runtime-api/std",