Migrate parachain swaps to Coretime (#3714)

This PR notifies broker pallet for any parachain slot swaps performed on
the relay chain. This is achieved by registering an `OnSwap` for the the
`coretime` pallet. The hook sends XCM message to the broker chain and
invokes a new extrinsic `swap_leases` which updates `Leases` storage
item (which keeps the legacy parachain leases).

I made two assumptions in this PR:
1.
[`Leases`](https://github.com/paritytech/polkadot-sdk/blob/4987d7982461e2e5ffe219cdf71ec697284cea7c/substrate/frame/broker/src/lib.rs#L120)
in `broker` pallet and
[`Leases`](https://github.com/paritytech/polkadot-sdk/blob/4987d7982461e2e5ffe219cdf71ec697284cea7c/polkadot/runtime/common/src/slots/mod.rs#L118)
in `slots` pallet are in sync.
2. `swap_leases` extrinsic from `broker` pallet can be triggered only by
root or by the XCM message from the relay chain. If not - the extrinsic
will generate an error and do nothing.

As a side effect from the changes `OnSwap` trait is moved from
runtime/common/traits.rs to runtime/parachains. Otherwise it is not
accessible from `broker` pallet.

Closes https://github.com/paritytech/polkadot-sdk/issues/3552

TODOs:

- [x] Weights
- [x] Tests

---------

Co-authored-by: command-bot <>
Co-authored-by: eskimor <eskimor@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

polkadot/runtime/rococo/src/lib.rs

@@ -38,7 +38,7 @@ use runtime_common::{
 		LocatableAssetConverter, ToAuthor, VersionedLocatableAsset, VersionedLocationConverter,
 	},
 	paras_registrar, paras_sudo_wrapper, prod_or_fast, slots,
-	traits::Leaser,
+	traits::{Leaser, OnSwap},
 	BlockHashCount, BlockLength, SlowAdjustingFeeUpdate,
 };
 use scale_info::TypeInfo;
@@ -1078,7 +1078,7 @@ impl paras_registrar::Config for Runtime {
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeEvent = RuntimeEvent;
 	type Currency = Balances;
-	type OnSwap = (Crowdloan, Slots);
+	type OnSwap = (Crowdloan, Slots, SwapLeases);
 	type ParaDeposit = ParaDeposit;
 	type DataDepositPerByte = DataDepositPerByte;
 	type WeightInfo = weights::runtime_common_paras_registrar::WeightInfo<Runtime>;
@@ -1306,6 +1306,14 @@ impl pallet_asset_rate::Config for Runtime {
 	type BenchmarkHelper = runtime_common::impls::benchmarks::AssetRateArguments;
 }
 
+// Notify `coretime` pallet when a lease swap occurs
+pub struct SwapLeases;
+impl OnSwap for SwapLeases {
+	fn on_swap(one: ParaId, other: ParaId) {
+		coretime::Pallet::<Runtime>::on_legacy_lease_swap(one, other);
+	}
+}
+
 construct_runtime! {
 	pub enum Runtime
 	{