Align the type of `AssetId`

[Dengjianping]

Currently, there're several AssetIds in manta-pay, like

StandardAssetId(manta-pay): u32
CalamariAssetId/DolphinAssetId
manta_accounting::asset::AssetId: struct AssetId(AssetIdType), AssetIdType: u32
pallet_assets::AssetId: generic type, finally it's u32
asset-manager::AssetId: generic type, finally it's u32

These types make me confused, hope it can be aligned.

[Garandor]

Calamari/Dolphin was necessary while Calamari didn't have mantapay, it's obsolete now so we can merge these or consider getting rid of dolphin as discussed in #958

StandardAssetId is the private ledger asset ID which is not necessarily the same as the public ledger CalamariAssetId, we should keep the distinction but we can improve the naming

The other ones are generics used by the pallets that we don't have influence over.

I would add a renaming of these types to 4.0.1 scope