Treasury spends various asset kinds (#1333)

### Summary 

This PR introduces new dispatchables to the treasury pallet, allowing
spends of various asset types. The enhanced features of the treasury
pallet, in conjunction with the asset-rate pallet, are set up and
enabled for Westend and Rococo.

### Westend and Rococo runtimes.

Polkadot/Kusams/Rococo Treasury can accept proposals for `spends` of
various asset kinds by specifying the asset's location and ID.

#### Treasury Instance New Dispatchables:
- `spend(AssetKind, AssetBalance, Beneficiary, Option<ValidFrom>)` -
propose and approve a spend;
- `payout(SpendIndex)` - payout an approved spend or retry a failed
payout
- `check_payment(SpendIndex)` - check the status of a payout;
- `void_spend(SpendIndex)` - void previously approved spend;
> existing spend dispatchable renamed to spend_local

in this context, the `AssetKind` parameter contains the asset's location
and it's corresponding `asset_id`, for example:
`USDT` on `AssetHub`,
``` rust
location = MultiLocation(0, X1(Parachain(1000)))
asset_id = MultiLocation(0, X2(PalletInstance(50), GeneralIndex(1984)))
```

the `Beneficiary` parameter is a `MultiLocation` in the context of the
asset's location, for example
``` rust
// the Fellowship salary pallet's location / account
FellowshipSalaryPallet = MultiLocation(1, X2(Parachain(1001), PalletInstance(64)))
// or custom `AccountId`
Alice = MultiLocation(0, AccountId32(network: None, id: [1,...]))
```

the `AssetBalance` represents the amount of the `AssetKind` to be
transferred to the `Beneficiary`. For permission checks, the asset
amount is converted to the native amount and compared against the
maximum spendable amount determined by the commanding spend origin.

the `spend` dispatchable allows for batching spends with different
`ValidFrom` arguments, enabling milestone-based spending. If the
expectations tied to an approved spend are not met, it is possible to
void the spend later using the `void_spend` dispatchable.

Asset Rate Pallet provides the conversion rate from the `AssetKind` to
the native balance.

#### Asset Rate Instance Dispatchables:
- `create(AssetKind, Rate)` - initialize a conversion rate to the native
balance for the given asset
- `update(AssetKind, Rate)` - update the conversion rate to the native
balance for the given asset
- `remove(AssetKind)` - remove an existing conversion rate to the native
balance for the given asset

the pallet's dispatchables can be executed by the Root or Treasurer
origins.

### Treasury Pallet

Treasury Pallet can accept proposals for `spends` of various asset kinds
and pay them out through the implementation of the `Pay` trait.

New Dispatchables:
- `spend(Config::AssetKind, AssetBalance, Config::Beneficiary,
Option<ValidFrom>)` - propose and approve a spend;
- `payout(SpendIndex)` - payout an approved spend or retry a failed
payout;
- `check_payment(SpendIndex)` - check the status of a payout;
- `void_spend(SpendIndex)` - void previously approved spend;
> existing spend dispatchable renamed to spend_local

The parameters' types of the `spend` dispatchable exposed via the
pallet's `Config` and allows to propose and accept a spend of a certain
amount.

An approved spend can be claimed via the `payout` within the
`Config::SpendPeriod`. Clients provide an implementation of the `Pay`
trait which can pay an asset of the `AssetKind` to the `Beneficiary` in
`AssetBalance` units.

The implementation of the Pay trait might not have an immediate final
payment status, for example if implemented over `XCM` and the actual
transfer happens on a remote chain.

The `check_status` dispatchable can be executed to update the spend's
payment state and retry the `payout` if the payment has failed.

---------

Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: command-bot <>

substrate/frame/tips/src/tests.rs

@@ -29,7 +29,10 @@ use sp_storage::Storage;
 use frame_support::{
 	assert_noop, assert_ok, parameter_types,
 	storage::StoragePrefixedMap,
-	traits::{ConstU32, ConstU64, SortedMembers, StorageVersion},
+	traits::{
+		tokens::{PayFromAccount, UnityAssetBalanceConversion},
+		ConstU32, ConstU64, SortedMembers, StorageVersion,
+	},
 	PalletId,
 };
 
@@ -123,7 +126,10 @@ parameter_types! {
 	pub const Burn: Permill = Permill::from_percent(50);
 	pub const TreasuryPalletId: PalletId = PalletId(*b"py/trsry");
 	pub const TreasuryPalletId2: PalletId = PalletId(*b"py/trsr2");
+	pub TreasuryAccount: u128 = Treasury::account_id();
+	pub TreasuryInstance1Account: u128 = Treasury1::account_id();
 }
+
 impl pallet_treasury::Config for Test {
 	type PalletId = TreasuryPalletId;
 	type Currency = pallet_balances::Pallet<Test>;
@@ -141,6 +147,14 @@ impl pallet_treasury::Config for Test {
 	type SpendFunds = ();
 	type MaxApprovals = ConstU32<100>;
 	type SpendOrigin = frame_support::traits::NeverEnsureOrigin<u64>;
+	type AssetKind = ();
+	type Beneficiary = Self::AccountId;
+	type BeneficiaryLookup = IdentityLookup<Self::Beneficiary>;
+	type Paymaster = PayFromAccount<Balances, TreasuryAccount>;
+	type BalanceConverter = UnityAssetBalanceConversion;
+	type PayoutPeriod = ConstU64<10>;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkHelper = ();
 }
 
 impl pallet_treasury::Config<Instance1> for Test {
@@ -160,6 +174,14 @@ impl pallet_treasury::Config<Instance1> for Test {
 	type SpendFunds = ();
 	type MaxApprovals = ConstU32<100>;
 	type SpendOrigin = frame_support::traits::NeverEnsureOrigin<u64>;
+	type AssetKind = ();
+	type Beneficiary = Self::AccountId;
+	type BeneficiaryLookup = IdentityLookup<Self::Beneficiary>;
+	type Paymaster = PayFromAccount<Balances, TreasuryInstance1Account>;
+	type BalanceConverter = UnityAssetBalanceConversion;
+	type PayoutPeriod = ConstU64<10>;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkHelper = ();
 }
 
 parameter_types! {