Westend/Rococo Asset Hub: pay xcm fees with sufficient assets (#2978)

Set up the `TakeFirstAssetTrader` trader for Westend and Rococo Asset
Hubs to cover XCM fees with sufficient assets.

This PR reintroduces previously
[removed](https://github.com/paritytech/polkadot-sdk/pull/1845) trader
setups, as it was decided to keep both traders, `TakeFirstAssetTrader`
and `SwapFirstAssetTrader`, during the transition period.

---------

Co-authored-by: Svyatoslav Nikolsky <svyatonik@gmail.com>

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/xcm_config.rs

@@ -585,6 +585,32 @@ impl xcm_executor::Config for XcmConfig {
 			ResolveAssetTo<StakingPot, crate::NativeAndAssets>,
 			AccountId,
 		>,
+		// This trader allows to pay with `is_sufficient=true` "Trust Backed" assets from dedicated
+		// `pallet_assets` instance - `Assets`.
+		cumulus_primitives_utility::TakeFirstAssetTrader<
+			AccountId,
+			AssetFeeAsExistentialDepositMultiplierFeeCharger,
+			TrustBackedAssetsConvertedConcreteId,
+			Assets,
+			cumulus_primitives_utility::XcmFeesTo32ByteAccount<
+				FungiblesTransactor,
+				AccountId,
+				XcmAssetFeesReceiver,
+			>,
+		>,
+		// This trader allows to pay with `is_sufficient=true` "Foreign" assets from dedicated
+		// `pallet_assets` instance - `ForeignAssets`.
+		cumulus_primitives_utility::TakeFirstAssetTrader<
+			AccountId,
+			ForeignAssetFeeAsExistentialDepositMultiplierFeeCharger,
+			ForeignAssetsConvertedConcreteId,
+			ForeignAssets,
+			cumulus_primitives_utility::XcmFeesTo32ByteAccount<
+				ForeignFungiblesTransactor,
+				AccountId,
+				XcmAssetFeesReceiver,
+			>,
+		>,
 	);
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;