Typesafe MultiAsset Wildcards

[gavofyork]

Right now, wildcard MultiAsset values (which are entirely indefinite and dependent on some context) are expressed by the same type as definite MultiAsset values. This leads to issues where items are accidentally not handled since indefinite wildcard values are unresolved at the time of handling and erroneously ignored.

To combat this, there should a new type WildMultiAsset which alone can express indefinite wildcard values. This is what would be typically used in XCM, but most internal functions would continue to operate on MultiAsset values (which will be altered so that it can only express definite assets). A WildMultiAsset::resolve function would convert one to the other, given a context, which would typically be the holding account.

This would probably be best combined with the move to the new MultiAsset (#2815).

[apopiak]

Is this fully addressed by #2815 ?

[KiChjang]

I believe this is fully resolved as of XCM v3.