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 <>

Cargo.lock

@@ -840,20 +840,27 @@ version = "1.0.0"
 dependencies = [
  "assert_matches",
  "asset-hub-westend-runtime",
+ "cumulus-pallet-dmp-queue",
+ "cumulus-pallet-parachain-system",
  "frame-support",
  "frame-system",
  "integration-tests-common",
  "pallet-asset-conversion",
+ "pallet-asset-rate",
  "pallet-assets",
  "pallet-balances",
+ "pallet-treasury",
  "pallet-xcm",
  "parachains-common",
  "parity-scale-codec",
  "polkadot-core-primitives",
  "polkadot-parachain-primitives",
+ "polkadot-runtime-common",
  "polkadot-runtime-parachains",
  "sp-runtime",
  "staging-xcm",
+ "staging-xcm-builder",
+ "staging-xcm-executor",
  "xcm-emulator",
 ]
 
@@ -10567,6 +10574,7 @@ dependencies = [
 name = "pallet-treasury"
 version = "4.0.0-dev"
 dependencies = [
+ "docify",
  "frame-benchmarking",
  "frame-support",
  "frame-system",
@@ -12485,6 +12493,7 @@ dependencies = [
  "impl-trait-for-tuples",
  "libsecp256k1",
  "log",
+ "pallet-asset-rate",
  "pallet-authorship",
  "pallet-babe",
  "pallet-balances",
@@ -12519,6 +12528,7 @@ dependencies = [
  "sp-staking",
  "sp-std",
  "staging-xcm",
+ "staging-xcm-builder",
  "static_assertions",
 ]
 
@@ -13900,6 +13910,7 @@ dependencies = [
  "frame-try-runtime",
  "hex-literal",
  "log",
+ "pallet-asset-rate",
  "pallet-authority-discovery",
  "pallet-authorship",
  "pallet-babe",
@@ -19941,6 +19952,7 @@ dependencies = [
  "frame-try-runtime",
  "hex-literal",
  "log",
+ "pallet-asset-rate",
  "pallet-authority-discovery",
  "pallet-authorship",
  "pallet-babe",