feat: assign change utxo index in transaction

[Temasar1]

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[twwu123]

I'm trying to think if this naive approach would end up making redeemer indexes wrong in this case. My initial thought is that it will mess up spending redeemer indexes.

[twwu123]

I was sort of thinking of a different approach where a txOut can be flagged as the change output, then the builder simply adds all remaining value to that specific output. But it makes it harder in the case where the change output has too many tokens and needs to be split into multiple utxos.