Introduce XcmFeesToAccount fee manager (#1234)

Combination of paritytech/polkadot#7005, its addon PR
paritytech/polkadot#7585 and its companion paritytech/cumulus#2433.

This PR introduces a new XcmFeesToAccount struct which implements the
`FeeManager` trait, and assigns this struct as the `FeeManager` in the
XCM config for all runtimes.

The struct simply deposits all fees handled by the XCM executor to a
specified account. In all runtimes, the specified account is configured
as the treasury account.

XCM __delivery__ fees are now being introduced (unless the root origin
is sending a message to a system parachain on behalf of the originating
chain).

# Note for reviewers

Most file changes are tests that had to be modified to account for the
new fees.
Main changes are in:
- cumulus/pallets/xcmp-queue/src/lib.rs <- To make it track the delivery
fees exponential factor
- polkadot/xcm/xcm-builder/src/fee_handling.rs <- Added. Has the
FeeManager implementation
- All runtime xcm_config files <- To add the FeeManager to the XCM
configuration

# Important note

After this change, instructions that create and send a new XCM (Query*,
Report*, ExportMessage, InitiateReserveWithdraw, InitiateTeleport,
DepositReserveAsset, TransferReserveAsset, LockAsset and RequestUnlock)
will require the corresponding origin account in the origin register to
pay for transport delivery fees, and the onward message will fail to be
sent if the origin account does not have the required amount. This
delivery fee is on top of what we already collect as tx fees in
pallet-xcm and XCM BuyExecution fees!

Wallet UIs that want to expose the new delivery fee can do so using the
formula:

```
delivery_fee_factor * (base_fee + encoded_msg_len * per_byte_fee)
```

where the delivery fee factor can be obtained from the corresponding
pallet based on which transport you are using (UMP, HRMP or bridges),
the base fee is a constant, the encoded message length from the message
itself and the per byte fee is the same as the configured per byte fee
for txs (i.e. `TransactionByteFee`).

---------

Co-authored-by: Branislav Kontur <bkontur@gmail.com>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Giles Cope <gilescope@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

cumulus/parachains/runtimes/assets/test-utils/src/test_cases.rs

@@ -15,10 +15,13 @@
 
 //! Module contains predefined test-case scenarios for `Runtime` with various assets.
 
+use super::xcm_helpers;
 use codec::Encode;
 use frame_support::{
 	assert_noop, assert_ok,
-	traits::{fungibles::InspectEnumerable, Get, OnFinalize, OnInitialize, OriginTrait},
+	traits::{
+		fungible::Mutate, fungibles::InspectEnumerable, Get, OnFinalize, OnInitialize, OriginTrait,
+	},
 	weights::Weight,
 };
 use frame_system::pallet_prelude::BlockNumberFor;
@@ -175,6 +178,21 @@ pub fn teleports_for_native_asset_works<
 						target_account_balance_before_teleport - existential_deposit
 				);
 
+				// Mint funds into account to ensure it has enough balance to pay delivery fees
+				let delivery_fees =
+					xcm_helpers::transfer_assets_delivery_fees::<XcmConfig::XcmSender>(
+						(native_asset_id, native_asset_to_teleport_away.into()).into(),
+						0,
+						Unlimited,
+						dest_beneficiary,
+						dest,
+					);
+				<pallet_balances::Pallet<Runtime>>::mint_into(
+					&target_account,
+					delivery_fees.into(),
+				)
+				.unwrap();
+
 				assert_ok!(RuntimeHelper::<Runtime>::do_teleport_assets::<HrmpChannelOpener>(
 					RuntimeHelper::<Runtime>::origin_of(target_account.clone()),
 					dest,
@@ -184,6 +202,7 @@ pub fn teleports_for_native_asset_works<
 					included_head.clone(),
 					&alice,
 				));
+
 				// check balances
 				assert_eq!(
 					<pallet_balances::Pallet<Runtime>>::free_balance(&target_account),
@@ -232,10 +251,21 @@ pub fn teleports_for_native_asset_works<
 					&alice,
 				));
 
+				let delivery_fees =
+					xcm_helpers::transfer_assets_delivery_fees::<XcmConfig::XcmSender>(
+						(native_asset_id, native_asset_to_teleport_away.into()).into(),
+						0,
+						Unlimited,
+						dest_beneficiary,
+						dest,
+					);
+
 				// check balances
 				assert_eq!(
 					<pallet_balances::Pallet<Runtime>>::free_balance(&target_account),
-					target_account_balance_before_teleport - native_asset_to_teleport_away
+					target_account_balance_before_teleport -
+						native_asset_to_teleport_away -
+						delivery_fees.into()
 				);
 				assert_eq!(
 					<pallet_balances::Pallet<Runtime>>::free_balance(&CheckingAccount::get()),
@@ -370,7 +400,7 @@ pub fn teleports_for_foreign_assets_works<
 		fun: Fungible(buy_execution_fee_amount),
 	};
 
-	let teleported_foreign_asset_amount = 10000000000000;
+	let teleported_foreign_asset_amount = 10_000_000_000_000;
 	let runtime_para_id = 1000;
 	ExtBuilder::<Runtime>::default()
 		.with_collators(collator_session_keys.collators())
@@ -400,11 +430,11 @@ pub fn teleports_for_foreign_assets_works<
 				<pallet_balances::Pallet<Runtime>>::free_balance(&target_account),
 				existential_deposit
 			);
+			// check `CheckingAccount` before
 			assert_eq!(
 				<pallet_balances::Pallet<Runtime>>::free_balance(&CheckingAccount::get()),
 				existential_deposit
 			);
-			// check `CheckingAccount` before
 			assert_eq!(
 				<pallet_assets::Pallet<Runtime, ForeignAssetsPalletInstance>>::balance(
 					foreign_asset_id_multilocation.into(),
@@ -540,6 +570,21 @@ pub fn teleports_for_foreign_assets_works<
 						.into()
 				);
 
+				// Make sure the target account has enough native asset to pay for delivery fees
+				let delivery_fees =
+					xcm_helpers::transfer_assets_delivery_fees::<XcmConfig::XcmSender>(
+						(foreign_asset_id_multilocation, asset_to_teleport_away).into(),
+						0,
+						Unlimited,
+						dest_beneficiary,
+						dest,
+					);
+				<pallet_balances::Pallet<Runtime>>::mint_into(
+					&target_account,
+					delivery_fees.into(),
+				)
+				.unwrap();
+
 				assert_ok!(RuntimeHelper::<Runtime>::do_teleport_assets::<HrmpChannelOpener>(
 					RuntimeHelper::<Runtime>::origin_of(target_account.clone()),
 					dest,