Remove All Assets and Uniques from NonTransfer Proxy

[shawntabrizi]

Given the nature of the Assets and Uniques pallet, it seems very sensible to disable all access to this pallets from the NonTransfer proxy.

Combinations of calls like mint and burn can be used to emulate transfer behaviors, and who knows what new functions will be added.

Given that we have explicit Proxies for AssetOwner and AssetManager, which specifically handle management of these pallets, I see little reason for NonTransfer proxy to have this risk.

Fixes: https://github.com/paritytech/srlabs_findings/issues/91

[xlc]

Not really directly related but I am thinking if it make sense to introduce an event based proxy filtering mechanism. i.e. fail the transaction if a specific event is emitted.

[shawntabrizi]

@xlc would only work for transactional extrinsics?

[xlc]

Right. So that't depends on making everything transactional first.
Another way could be annotate each calls with tags and filter based on whitelist / blacklist of the tags. I guess this won't happen though... But the current proxy filter is really error prone.

[bkchr]

Unique is not in statemint and westmint?

[shawntabrizi]

@bkchr nope. should it be?

EDIT: #493

[shawntabrizi]

bot merge

[ghost]

Trying merge.