`outgoing_tx_data.to_address` should not carry UA

[AArnott]

Why is zingolib providing the compound UA in the to_address field, leaving the recipient_ua field empty for a transaction's outgoing_tx_data? I expected the to_address to always be the literal address used in the transaction, and if Zingolib is going to preserve the UA's other receivers in the change memo, that that would only appear under recipient_ua