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 <[email protected]>

* Add missing on_runtime_upgrade implementation

* Use new migration API

* cargo fmt

* Fix log message

Co-authored-by: Oliver Tale-Yazdi <[email protected]>