Cleanup XCMP QueueConfigData (#2142)

Removes obsolete fields from the `QueueConfigData` structure. For the
remaining fields, if they use the old defaults, we replace them with the
new defaults.

Resolves: https://github.com/paritytech/polkadot-sdk/issues/1795

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs

@@ -118,6 +118,8 @@ pub type Migrations = (
 	pallet_collator_selection::migration::v1::MigrateToV1<Runtime>,
 	pallet_multisig::migrations::v1::MigrateToV1<Runtime>,
 	InitStorageVersions,
+	// unreleased
+	cumulus_pallet_xcmp_queue::migration::v4::MigrationToV4<Runtime>,
 );
 
 /// Migration to initialize storage versions for pallets added after genesis.