Refactor replacement outputs to be an Iterator of ref TxOuts

[benalleng]

We can pass the replacement outputs as a ref Iterator instead of using a Vec of TxOuts.

Same as before I guess the question is whether this is really needed especially considering how little was affected downstream by this arg type change.

Perhaps its still useful to convert this to an Iterator and not a reference but I'm not totally sure, especially since in my approach I end up just converting it back to a Vec to work with interleave_shuffle better

[coveralls]

Pull Request Test Coverage Report for Build 13166226056

Details

• 8 of 14 (57.14%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 79.08%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
payjoin/src/receive/v2/mod.rs	0	6	0.0%

Totals
Change from base Build 13161838713:	0.0%
Covered Lines:	3765
Relevant Lines:	4761

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💛 - Coveralls

[spacebear21]

Similar to #527 I think using references here adds complexity for unclear benefits.

I'd be fine with changing it to replacement_outputs: impl IntoIterator<Item = TxOut>, if interleave_shuffle can be made to work with the same type. But if we're converting back into a Vec anyway it's probably not worth it.

[DanGould]

The reason to do it here is different than just changing ownership to a ref. Perhaps the iterator is a db struct and not an in-memory Vec, which is where a more generic interface is helpful. I did some LLMing to get interleave_shuffle to also take an interator which is I think what needs to happen to realize the generalization here