[MultiParentchain] add CI test including a Target A&B parentchains

[clangenb]

This is not tested yet, although a demo script already exists. It should be a minimal effort to launch a second node with the docker compose and run the already existing script

[brenzi]

Astar uses zombienet in CI: https://github.com/AstarNetwork/Astar/blob/298a8e413874b0bcd36fe1316a55217ee3906d4d/.github/workflows/zombienetRpcTest.yml
Moonbeam too:
https://github.com/moonbeam-foundation/moonbeam/tree/master/test
manta (rather simple setup):
https://github.com/Manta-Network/manta-indexer/pull/30/files