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>

substrate/frame/broker/src/lib.rs

@@ -786,5 +786,13 @@ pub mod pallet {
 			Self::do_notify_core_count(core_count)?;
 			Ok(())
 		}
+
+		#[pallet::call_index(99)]
+		#[pallet::weight(T::WeightInfo::swap_leases())]
+		pub fn swap_leases(origin: OriginFor<T>, id: TaskId, other: TaskId) -> DispatchResult {
+			T::AdminOrigin::ensure_origin_or_root(origin)?;
+			Self::do_swap_leases(id, other)?;
+			Ok(())
+		}
 	}
 }