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>

cumulus/parachains/integration-tests/emulated/chains/relays/rococo/src/lib.rs

@@ -39,6 +39,8 @@ decl_test_relay_chains! {
 			Hrmp: rococo_runtime::Hrmp,
 			Identity: rococo_runtime::Identity,
 			IdentityMigrator: rococo_runtime::IdentityMigrator,
+			Treasury: rococo_runtime::Treasury,
+			AssetRate: rococo_runtime::AssetRate,
 		}
 	},
 }