Return type of output_asset_to changed to Address

[dmihal]

Description

When output_asset_to was added in #4694, it used b256 as the return type, instead of an Address. It referenced #4569, which describes the confusion developers face between Address and Identity.

While that confusion is an issue, I don't believe that's relevant to this function type. An output coin can only be an address, not a contract, since contract balances are stored in the contract UTXO itself. Furthermore, the standard lib API will need to be frozen soon, and there's no plans in place to change anything in regards to #4569.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[bitzoic]

This makes sense to me! Also very cool to see our first practical implementation of order-independent modules since #5300 has been merged 🔥

[bitzoic]