anomac transfer should support multitoken transfers

[james-chf]

We will want accounts on Anoma which handle the ledgers for more than one token, for example this is how wrapped ERC20 assets will be kept track of. (#114)

#<eth-bridge-bech32m-address>/ERC20/<erc20-ethereum-address>/balance/<owner-bech32m-address> : Amount

e.g.

#atest1v4ehgw36g4pyg3j9x3qnjd3cxgmyz3fk8qcrys3hxdp5xwfnx3zyxsj9xgunxsfjg5u5xvzyzrrqtn/ERC20/0x6B175474E89094C44Da98b954EedeAC495271d0F/balance/atest1d9khqw36x9zyxwfhgfpygv2pgc65gse4gy6rjs34gfzr2v69gy6y23zpggurjv2yx5m52sesu6r4y4

More generally we want to support transfers for any arbitrary "/balance/` key suffix that isn't necessarily top level. So in general we could have multitoken accounts like

#<some-top-level-bech32m-address>/.../<token-id>/balance/<owner-bech32m-address>

This issue is to update anomac transfer to work with such multitokens, specifically we need a tx wasm that does the transfer correctly - the validity predicate(s) for validating that such a transfer happened is out of scope for this issue and may differ slightly between different multitokens.

One way would do this issue would be to update the existing tx_transfer to work with any arbitrary storage key prefix (e.g. #<eth-bridge-bech32m-address>/erc20/<erc20-ethereum-address>/...) rather than a top-level Anoma address. Alternatively we could make a new separate tx_multitoken_transfer that the anomac transfer should delegate to using in the case of multitoken transfers.