Migrate assets pallet to new macros

[dvdplm]

Converts the Assets pallet to the new pallet attribute macro introduced in #6877.

Part of #7882.

Upgrade guidelines used.

⚠️ Breaking Change ⚠️

From https://crates.parity.io/frame_support/attr.pallet.html#checking-upgrade-guidelines

storages now use PalletInfo for module_prefix instead of the one given to decl_storage: use of this pallet in construct_runtime! needs careful updating of the name in order to not break storage or to upgrade storage (moreover for instantiable pallet). If pallet is published, make sure to warn about this breaking change.

So users of the Assets pallet must be careful about the name they used in construct_runtime!. Hence the runtime-migration label, which might not be needed depending on the configuration of the Assets pallet.

[dvdplm]

@ascjones Do you know how we should handle the deprecation of RawEvent? Should we still provide the type alias or rather try to track down uses and update (or both)?

[gui1117]

@ascjones Do you know how we should handle the deprecation of RawEvent? Should we still provide the type alias or rather try to track down uses and update (or both)?

we can also have a deprecated alias. This could help other to migrate.

before this PR raw event was:

enum RawEvent<AccountId, Balance, AssetId> {...};
type Event<C: Config> = RawEvent<C::AccounId,...>;

Maybe we can now do:

#[deprecated(...)]
type RawEvent<T> = Event<T>;

But at the same time this is a breaking RawEvent as its generic are different

[dvdplm]

But at the same time this is a breaking RawEvent as its generic are different

Right, so people would get a compiler error and also the deprecation message? That seems good.

[ascjones]

LGTM 🚀

[gui1117]

bot merge

[ghost]

Trying merge.

[dvdplm]

@thiolliere I added the D1-runtime-migration label here but I don't think that is actually needed for pallet-assets (not used in Polkadot). Do you agree?

[gui1117]

@thiolliere I added the D1-runtime-migration label here but I don't think that is actually needed for pallet-assets (not used in Polkadot). Do you agree?

Yes I think it is better to have all the commit with potential need for migration labelled as such. It is useful for other builders