Simplify multi-asset value conversions.

[jonathanknowles]

Issue

None. Noticed while browsing the code.

Summary

This PR makes the following simplification in several places:

- fromCardanoValue . Cardano.fromMaryValue
+ toWalletTokenBundle

The original expression performs a two-step conversion of multi-asset (MA) values:

1. From a cardano-ledger MA value (nested map) to a cardano-api MA value (flat map)
2. From a cardano-api MA value (flat map) to a cardano-wallet MA value (nested map)

The toWalletTokenBundle function performs this conversion in a single step, and doesn't require the creation of an intermediate cardano-api MA value.

[paweljakubas]

👍

[Anviking]

This may risk entangling the wallet and cardano-balance-tx more, but it may be worth it as it is better 🤔

[jonathanknowles]

This may risk entangling the wallet and cardano-balance-tx more, but it may be worth it as it is better 🤔

I was thinking it could make things easier, as the dependency set of this particular conversion has been reduced in the following way:

- {cardano-wallet-primitive, cardano-ledger, cardano-api}
+ {cardano-wallet-primitive, cardano-ledger}

In other words, if we have a ledger value, or a primitive value, we'd no longer need to go via the equivalent cardano-api value when converting.

OTOH, much of the balanceTransaction API makes use of cardano-api types. Perhaps it would be worth having a discussion on which set of types we'd prefer to depend upon?

[Anviking]

On second thought I really don't think there's a meaningful drawback with this in particular, but happy to discuss tomorrow anyway. My concern would be where Compatibility.Ledger would live now / in the future and who'd depend on it.