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/starters/shell/src/xcm_config.rs

@@ -18,8 +18,8 @@ use super::{
 	RuntimeOrigin,
 };
 use frame_support::{
-	match_types, parameter_types,
-	traits::{Everything, Nothing},
+	parameter_types,
+	traits::{Contains, Everything, Nothing},
 	weights::Weight,
 };
 use xcm::latest::prelude::*;
@@ -29,9 +29,9 @@ use xcm_builder::{
 };
 
 parameter_types! {
-	pub const RococoLocation: MultiLocation = MultiLocation::parent();
+	pub const RococoLocation: Location = Location::parent();
 	pub const RococoNetwork: Option<NetworkId> = Some(NetworkId::Rococo);
-	pub UniversalLocation: InteriorMultiLocation = X1(Parachain(ParachainInfo::parachain_id().into()));
+	pub UniversalLocation: InteriorLocation = [Parachain(ParachainInfo::parachain_id().into())].into();
 }
 
 /// This is the type we use to convert an (incoming) XCM origin into a local `Origin` instance,
@@ -47,8 +47,11 @@ pub type XcmOriginToTransactDispatchOrigin = (
 	ParentAsSuperuser<RuntimeOrigin>,
 );
 
-match_types! {
-	pub type JustTheParent: impl Contains<MultiLocation> = { MultiLocation { parents:1, interior: Here } };
+pub struct JustTheParent;
+impl Contains<Location> for JustTheParent {
+	fn contains(location: &Location) -> bool {
+		matches!(location.unpack(), (1, []))
+	}
 }
 
 parameter_types! {