Add Rococo People <> Rococo Bulletin bridge support to Rococo Bridge Hub (#2540)

This PR adds [Rococo
People](https://github.com/paritytech/polkadot-sdk/pull/2281) <> [Rococo
Bulletin](https://github.com/zdave-parity/polkadot-bulletin-chain) to
the Rococo Bridge Hub code. There's a couple of things left to do here:
- [x] add remaining tests - it'd need some refactoring in the
`bridge-hub-test-utils` - will do in a separate PR;
- [x] actually run benchmarks for new messaging pallet (do we have bot
nowadays?).

The reason why I'm opening it before this ^^^ is ready, is that I'd like
to hear others opinion on how to deal with hacks with that bridge.
Initially I was assuming that Rococo Bulletin will be the 1:1 copy of
the Polkadot Bulletin (to avoid maintaining multiple
runtimes/releases/...), so you can see many `PolkadotBulletin` mentions
in this PR, even though we are going to bridge with the parallel chain
(`RococoBulletin`). That's because e.g. pallet names from
`construct_runtime` are affecting runtime storage keys and bridges are
using runtime storage proofs => it is important to use names that the
Bulletin chain expects.

But in the end, this hack won't work - we can't use Polkadot Bulletin
runtime to bridge with Rococo Bridge Hub, because Polkadot Bulletin
expects Polkadot Bridge hub to use `1002` parachain id and Rococo Bridge
Hub seats on the `1013`. This also affects storage keys using in
bridging, so I had to add the [`rococo`
feature](https://github.com/svyatonik/polkadot-bulletin-chain/blob/add-bridge-pallets/runtime/Cargo.toml#L198)
to the Bulletin chain. So now we can actually alter its runtime and
adapt it for Rococo.

So the question here is - what's better for us here
- to leave everything as is (seems hacky and non-trivial);
- change Bulletin chain runtime when `rococo` feature is used - e.g. use
proper names there (`WithPolkadotGrandpa` -> `WithRococoGrandpa`, ...)
- add another set of pallets to the Bulletin chain runtime to bridge
with Rococo and never use them in production. Similar to hack that we
had in Rococo/Wococo

cc @acatangiu @bkontur @serban300 

also cc @joepetrowski as the main "client" of this bridge

---

A couple words on how this bridge is different from the Rococo <>
Westend bridge:
- it is a bridge with a chain that uses GRANDPA finality, not the
parachain finality (hence the tests needs to be changed);
- it is a fee-free bridge. So
`AllowExplicitUnpaidExecutionFrom<Equals<SiblingPeople>>` + we are not
paying any rewards to relayers (apart from compensating transaction
costs).

---------

Signed-off-by: dependabot[bot] <support@github.com>
Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
Co-authored-by: Adrian Catangiu <adrian@parity.io>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>
Co-authored-by: Egor_P <egor@parity.io>
Co-authored-by: command-bot <>

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -20,7 +20,8 @@ use super::{
 	TransactionByteFee, WeightToFee, XcmpQueue,
 };
 use crate::bridge_common_config::{
-	BridgeGrandpaWestendInstance, DeliveryRewardInBalance, RequiredStakeForStakeAndSlash,
+	BridgeGrandpaRococoBulletinInstance, BridgeGrandpaWestendInstance, DeliveryRewardInBalance,
+	RequiredStakeForStakeAndSlash,
 };
 use bp_messages::LaneId;
 use bp_relayers::{PayRewardFromAccount, RewardsAccountOwner, RewardsAccountParams};
@@ -72,6 +73,7 @@ parameter_types! {
 	pub const MaxAssetsIntoHolding: u32 = 64;
 	pub TreasuryAccount: AccountId = TREASURY_PALLET_ID.into_account_truncating();
 	pub RelayTreasuryLocation: MultiLocation = (Parent, PalletInstance(rococo_runtime_constants::TREASURY_PALLET_ID)).into();
+	pub SiblingPeople: MultiLocation = (Parent, Parachain(rococo_runtime_constants::system_parachain::PEOPLE_ID)).into();
 }
 
 /// Type for specifying how a `MultiLocation` can be converted into an `AccountId`. This is used
@@ -187,6 +189,10 @@ impl Contains<RuntimeCall> for SafeCallFilter {
 				RuntimeCall::BridgeWestendGrandpa(pallet_bridge_grandpa::Call::<
 					Runtime,
 					BridgeGrandpaWestendInstance,
+				>::initialize { .. }) |
+				RuntimeCall::BridgePolkadotBulletinGrandpa(pallet_bridge_grandpa::Call::<
+					Runtime,
+					BridgeGrandpaRococoBulletinInstance,
 				>::initialize { .. })
 		)
 	}
@@ -205,11 +211,12 @@ pub type Barrier = TrailingSetTopicAsId<
 					// If the message is one that immediately attempts to pay for execution, then
 					// allow it.
 					AllowTopLevelPaidExecutionFrom<Everything>,
-					// Parent, its pluralities (i.e. governance bodies) and relay treasury pallet
-					// get free execution.
+					// Parent, its pluralities (i.e. governance bodies), relay treasury pallet
+					// and sibling People get free execution.
 					AllowExplicitUnpaidExecutionFrom<(
 						ParentOrParentsPlurality,
 						Equals<RelayTreasuryLocation>,
+						Equals<SiblingPeople>,
 					)>,
 					// Subscriptions for version tracking are OK.
 					AllowSubscriptionsFrom<ParentRelayOrSiblingParachains>,
@@ -273,7 +280,10 @@ impl xcm_executor::Config for XcmConfig {
 			XcmFeeToAccount<Self::AssetTransactor, AccountId, TreasuryAccount>,
 		),
 	>;
-	type MessageExporter = (crate::bridge_to_westend_config::ToBridgeHubWestendHaulBlobExporter,);
+	type MessageExporter = (
+		crate::bridge_to_westend_config::ToBridgeHubWestendHaulBlobExporter,
+		crate::bridge_to_bulletin_config::ToRococoBulletinHaulBlobExporter,
+	);
 	type UniversalAliases = Nothing;
 	type CallDispatcher = WithOriginFilter<SafeCallFilter>;
 	type SafeCallFilter = SafeCallFilter;