Remove xcm::v3 from assets-common nits (#4037)

This PR mainly removes `xcm::v3` stuff from `assets-common` to make it
more generic and facilitate the transition to newer XCM versions. Some
of the implementations here used hard-coded `xcm::v3::Location`, but now
it's up to the runtime to configure according to its needs.

Additional/consequent changes:
- `penpal` runtime uses now `xcm::latest::Location` for `pallet_assets`
as `AssetId`, because we don't care about migrations here
- it pretty much simplify xcm-emulator integration tests, where we don't
need now a lots of boilerplate conversions:
      ```
      v3::Location::try_from(...).expect("conversion works")`
      ```
- xcm-emulator tests
- split macro `impl_assets_helpers_for_parachain` to the
`impl_assets_helpers_for_parachain` and
`impl_foreign_assets_helpers_for_parachain` (avoids using hard-coded
`xcm::v3::Location`)

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

@@ -82,8 +82,6 @@ parameter_types! {
 		PalletInstance(<PoolAssets as PalletInfoAccess>::index() as u8).into();
 	pub UniquesPalletLocation: Location =
 		PalletInstance(<Uniques as PalletInfoAccess>::index() as u8).into();
-	pub PoolAssetsPalletLocationV3: xcm::v3::Location =
-		xcm::v3::Junction::PalletInstance(<PoolAssets as PalletInfoAccess>::index() as u8).into();
 	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
 	pub const GovernanceLocation: Location = Location::parent();
 	pub StakingPot: AccountId = CollatorSelection::account_id();
@@ -179,6 +177,7 @@ pub type ForeignAssetsConvertedConcreteId = assets_common::ForeignAssetsConverte
 		StartsWithExplicitGlobalConsensus<UniversalLocationNetworkId>,
 	),
 	Balance,
+	xcm::v3::Location,
 >;
 
 /// Means for transacting foreign assets from different global consensus.
@@ -581,7 +580,11 @@ impl xcm_executor::Config for XcmConfig {
 			WeightToFee,
 			crate::NativeAndAssets,
 			(
-				TrustBackedAssetsAsLocation<TrustBackedAssetsPalletLocation, Balance>,
+				TrustBackedAssetsAsLocation<
+					TrustBackedAssetsPalletLocation,
+					Balance,
+					xcm::v3::Location,
+				>,
 				ForeignAssetsConvertedConcreteId,
 			),
 			ResolveAssetTo<StakingPot, crate::NativeAndAssets>,