Make penpal-runtime's TrustedReserves more connfigurable (#3564)

The current `penpal` runtime utilizes the `EthereumLocation` parameter,
which is employed for XCM emulated integration tests concerning the
Rococo <> ETH bridge. It includes a hard-coded chainId for the Ethereum
testnet utilized in Rococo. The `EthereumLocation` serves the purpose of
aligning with the `TrustedReserves`. However, due to this hard-coded
configuration, reusing `penpal` for testing various environments such as
Kusama/Polkadot versus Ethereum bridge becomes unfeasible.

This PR introduces the capability to easily customize the asset location
for `TrustedReserves` without needing to know anything about Ethereum.


## TODO
- [x] fix integration tests with
`System::set_storage(CustomizableAssetFromSystemAssetHub::key(),
<whatever-location-is-needed>)` @claravanstaden
- [ ] ~~maybe add some helper function/macro to support `set_storage`
for other runtimes (that we could reuse)~~
- [ ] Release patch for: `penpal-runtime` + emulated crate with
`set_storage` support (if needed)
  - [ ] backport to 1.7.0
  - [ ] backport to 1.8.0

---------

Co-authored-by: Clara van Staden <claravanstaden64@gmail.com>

cumulus/parachains/runtimes/testing/penpal/Cargo.toml

@@ -77,7 +77,6 @@ cumulus-primitives-utility = { path = "../../../../primitives/utility", default-
 pallet-collator-selection = { path = "../../../../pallets/collator-selection", default-features = false }
 parachain-info = { package = "staging-parachain-info", path = "../../../pallets/parachain-info", default-features = false }
 parachains-common = { path = "../../../common", default-features = false }
-testnet-parachains-constants = { path = "../../constants", default-features = false, features = ["rococo"] }
 assets-common = { path = "../../assets/common", default-features = false }
 
 [features]
@@ -133,7 +132,6 @@ std = [
 	"sp-transaction-pool/std",
 	"sp-version/std",
 	"substrate-wasm-builder",
-	"testnet-parachains-constants/std",
 	"xcm-builder/std",
 	"xcm-executor/std",
 	"xcm/std",

cumulus/parachains/runtimes/testing/penpal/src/xcm_config.rs

@@ -43,7 +43,6 @@ use pallet_xcm::XcmPassthrough;
 use polkadot_parachain_primitives::primitives::Sibling;
 use polkadot_runtime_common::impls::ToAuthor;
 use sp_runtime::traits::Zero;
-use testnet_parachains_constants::rococo::snowbridge::EthereumNetwork;
 use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
@@ -295,7 +294,13 @@ parameter_types! {
 		0,
 		[xcm::v3::Junction::PalletInstance(50), xcm::v3::Junction::GeneralIndex(TELEPORTABLE_ASSET_ID.into())]
 	);
-	pub EthereumLocation: Location = Location::new(2, [GlobalConsensus(EthereumNetwork::get())]);
+
+	/// The Penpal runtime is utilized for testing with various environment setups.
+	/// This storage item provides the opportunity to customize testing scenarios
+	/// by configuring the trusted asset from the `SystemAssetHub`.
+	///
+	/// By default, it is configured as a `SystemAssetHubLocation` and can be modified using `System::set_storage`.
+	pub storage CustomizableAssetFromSystemAssetHub: Location = SystemAssetHubLocation::get();
 }
 
 /// Accepts asset with ID `AssetLocation` and is coming from `Origin` chain.
@@ -310,11 +315,11 @@ impl<AssetLocation: Get<Location>, Origin: Get<Location>> ContainsPair<Asset, Lo
 	}
 }
 
-pub type Reserves = (
+pub type TrustedReserves = (
 	NativeAsset,
 	AssetsFrom<SystemAssetHubLocation>,
 	NativeAssetFrom<SystemAssetHubLocation>,
-	AssetPrefixFrom<EthereumLocation, SystemAssetHubLocation>,
+	AssetPrefixFrom<CustomizableAssetFromSystemAssetHub, SystemAssetHubLocation>,
 );
 pub type TrustedTeleporters =
 	(AssetFromChain<LocalTeleportableToAssetHub, SystemAssetHubLocation>,);
@@ -326,7 +331,7 @@ impl xcm_executor::Config for XcmConfig {
 	// How to withdraw and deposit an asset.
 	type AssetTransactor = AssetTransactors;
 	type OriginConverter = XcmOriginToTransactDispatchOrigin;
-	type IsReserve = Reserves;
+	type IsReserve = TrustedReserves;
 	// no teleport trust established with other chains
 	type IsTeleporter = TrustedTeleporters;
 	type UniversalLocation = UniversalLocation;