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>