Added Rococo BH <> Rococo Bulletin bridge (#2724)

* added Rococo BH <> Rococo Bulletin bridge

* init-bridge support

* allow customising finality-related runtime APIs

* revert me

* use Rococo/BridgeHubRococo pretending to be a Polkadot/BridgeHubPolkadot in Rococo <> RococoBulletin bridge

* Revert "revert me"

This reverts commit 90c598d9.

* Revert "allow customising finality-related runtime APIs"

This reverts commit b39c32c3.

* fmt

* WITH_BRIDGE_ROCOCO_TO_BULLETIN_MESSAGES_PALLET_INDEX

* regenerate bulletin chain runtime (pallet indices have changed)

* fx WITH_BRIDGE_ROCOCO_TO_BULLETIN_MESSAGES_PALLET_INDEX constant because of latest changes

* also change indices in runtime

* fmt

* clippy