FRAME: Unity Balance Conversion for Different IDs of Native Asset (#3659)

Introduce types to define 1:1 balance conversion for different relative
asset ids/locations of native asset.

Examples:
native asset on Asset Hub presented as `VersionedLocatableAsset` type in
the context of Relay Chain is
```
{
  `location`: (0, Parachain(1000)),
  `asset_id`: (1, Here),
}
```
and it's balance should be converted 1:1 by implementations of
`ConversionToAssetBalance` trait.

---------

Co-authored-by: Branislav Kontur <bkontur@gmail.com>

polkadot/runtime/westend/src/lib.rs

@@ -31,9 +31,9 @@ use frame_support::{
 	genesis_builder_helper::{build_state, get_preset},
 	parameter_types,
 	traits::{
-		fungible::HoldConsideration, ConstU32, Contains, EitherOf, EitherOfDiverse, EverythingBut,
-		InstanceFilter, KeyOwnerProofSystem, LinearStoragePrice, ProcessMessage,
-		ProcessMessageError, WithdrawReasons,
+		fungible::HoldConsideration, tokens::UnityOrOuterConversion, ConstU32, Contains, EitherOf,
+		EitherOfDiverse, EverythingBut, FromContains, InstanceFilter, KeyOwnerProofSystem,
+		LinearStoragePrice, ProcessMessage, ProcessMessageError, WithdrawReasons,
 	},
 	weights::{ConstantMultiplier, WeightMeter, WeightToFee as _},
 	PalletId,
@@ -57,7 +57,8 @@ use runtime_common::{
 	elections::OnChainAccuracy,
 	identity_migrator, impl_runtime_weights,
 	impls::{
-		LocatableAssetConverter, ToAuthor, VersionedLocatableAsset, VersionedLocationConverter,
+		ContainsParts, LocatableAssetConverter, ToAuthor, VersionedLocatableAsset,
+		VersionedLocationConverter,
 	},
 	paras_registrar, paras_sudo_wrapper, prod_or_fast, slots,
 	traits::{Leaser, OnSwap},
@@ -80,7 +81,7 @@ use runtime_parachains::{
 	shared as parachains_shared,
 };
 use scale_info::TypeInfo;
-use sp_core::{OpaqueMetadata, RuntimeDebug, H256};
+use sp_core::{ConstU8, OpaqueMetadata, RuntimeDebug, H256};
 use sp_runtime::{
 	create_runtime_str,
 	curve::PiecewiseLinear,
@@ -712,7 +713,15 @@ impl pallet_treasury::Config for Runtime {
 		LocatableAssetConverter,
 		VersionedLocationConverter,
 	>;
-	type BalanceConverter = AssetRate;
+	type BalanceConverter = UnityOrOuterConversion<
+		ContainsParts<
+			FromContains<
+				xcm_builder::IsChildSystemParachain<ParaId>,
+				xcm_builder::IsParentsOnly<ConstU8<1>>,
+			>,
+		>,
+		AssetRate,
+	>;
 	type PayoutPeriod = PayoutSpendPeriod;
 	#[cfg(feature = "runtime-benchmarks")]
 	type BenchmarkHelper = runtime_common::impls::benchmarks::TreasuryArguments;