Properly migrate weights to v2 (#6091)

* Create migration for config pallet

* Use XcmWeight in XCM pallet extrinsics

* Link to PR in doc comment

* cargo fmt

* Fix tests

* Fix tests

* Remove unused import

* Update runtime/parachains/src/configuration/migration.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Add missing on_runtime_upgrade implementation

* Use new migration API

* cargo fmt

* Fix log message

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

polkadot/runtime/rococo/src/lib.rs

@@ -1453,6 +1453,7 @@ pub type Executive = frame_executive::Executive<
 	frame_system::ChainContext<Runtime>,
 	Runtime,
 	AllPalletsWithSystem,
+	(parachains_configuration::migration::v3::MigrateToV3<Runtime>,),
 >;
 /// The payload being signed in transactions.
 pub type SignedPayload = generic::SignedPayload<RuntimeCall, SignedExtra>;