XCMv4 (#1230)

# Note for reviewer

Most changes are just syntax changes necessary for the new version.
Most important files should be the ones under the `xcm` folder.

# Description 

Added XCMv4.

## Removed `Multi` prefix
The following types have been renamed:
- MultiLocation -> Location
- MultiAsset -> Asset
- MultiAssets -> Assets
- InteriorMultiLocation -> InteriorLocation
- MultiAssetFilter -> AssetFilter
- VersionedMultiAsset -> VersionedAsset
- WildMultiAsset -> WildAsset
- VersionedMultiLocation -> VersionedLocation

In order to fix a name conflict, the `Assets` in `xcm-executor` were
renamed to `HoldingAssets`, as they represent assets in holding.

## Removed `Abstract` asset id

It was not being used anywhere and this simplifies the code.

Now assets are just constructed as follows:

```rust
let asset: Asset = (AssetId(Location::new(1, Here)), 100u128).into();
```

No need for specifying `Concrete` anymore.

## Outcome is now a named fields struct

Instead of

```rust
pub enum Outcome {
  Complete(Weight),
  Incomplete(Weight, Error),
  Error(Error),
}
```

we now have

```rust
pub enum Outcome {
  Complete { used: Weight },
  Incomplete { used: Weight, error: Error },
  Error { error: Error },
}
```

## Added Reanchorable trait

Now both locations and assets implement this trait, making it easier to
reanchor both.

## New syntax for building locations and junctions

Now junctions are built using the following methods:

```rust
let location = Location {
    parents: 1,
    interior: [Parachain(1000), PalletInstance(50), GeneralIndex(1984)].into()
};
```

or

```rust
let location = Location::new(1, [Parachain(1000), PalletInstance(50), GeneralIndex(1984)]);
```

And they are matched like so:

```rust
match location.unpack() {
  (1, [Parachain(id)]) => ...
  (0, Here) => ...,
  (1, [_]) => ...,
}
```

This syntax is mandatory in v4, and has been also implemented for v2 and
v3 for easier migration.

This was needed to make all sizes smaller.

# TODO
- [x] Scaffold v4
- [x] Port github.com/paritytech/polkadot/pull/7236
- [x] Remove `Multi` prefix
- [x] Remove `Abstract` asset id

---------

Co-authored-by: command-bot <>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

cumulus/parachains/runtimes/collectives/collectives-westend/src/fellowship/mod.rs

@@ -43,7 +43,7 @@ use parachains_common::{
 	westend::{account, currency::GRAND},
 };
 use polkadot_runtime_common::impls::{
-	LocatableAssetConverter, VersionedLocatableAsset, VersionedMultiLocationConverter,
+	LocatableAssetConverter, VersionedLocatableAsset, VersionedLocationConverter,
 };
 use sp_arithmetic::Permill;
 use sp_core::{ConstU128, ConstU32};
@@ -202,7 +202,7 @@ pub type FellowshipSalaryInstance = pallet_salary::Instance1;
 parameter_types! {
 	// The interior location on AssetHub for the paying account. This is the Fellowship Salary
 	// pallet instance (which sits at index 64). This sovereign account will need funding.
-	pub Interior: InteriorMultiLocation = PalletInstance(64).into();
+	pub Interior: InteriorLocation = PalletInstance(64).into();
 }
 
 const USDT_UNITS: u128 = 1_000_000;
@@ -250,7 +250,7 @@ parameter_types! {
 	pub const MaxBalance: Balance = Balance::max_value();
 	// The asset's interior location for the paying account. This is the Fellowship Treasury
 	// pallet instance (which sits at index 65).
-	pub FellowshipTreasuryInteriorLocation: InteriorMultiLocation = PalletInstance(65).into();
+	pub FellowshipTreasuryInteriorLocation: InteriorLocation = PalletInstance(65).into();
 }
 
 #[cfg(feature = "runtime-benchmarks")]
@@ -269,10 +269,10 @@ pub type FellowshipTreasuryPaymaster = PayOverXcm<
 	crate::xcm_config::XcmRouter,
 	crate::PolkadotXcm,
 	ConstU32<{ 6 * HOURS }>,
-	VersionedMultiLocation,
+	VersionedLocation,
 	VersionedLocatableAsset,
 	LocatableAssetConverter,
-	VersionedMultiLocationConverter,
+	VersionedLocationConverter,
 >;
 
 pub type FellowshipTreasuryInstance = pallet_treasury::Instance1;
@@ -327,7 +327,7 @@ impl pallet_treasury::Config<FellowshipTreasuryInstance> for Runtime {
 		>,
 	>;
 	type AssetKind = VersionedLocatableAsset;
-	type Beneficiary = VersionedMultiLocation;
+	type Beneficiary = VersionedLocation;
 	type BeneficiaryLookup = IdentityLookup<Self::Beneficiary>;
 	#[cfg(not(feature = "runtime-benchmarks"))]
 	type Paymaster = FellowshipTreasuryPaymaster;