TxOdering::Shuffle is not shuffling the inputs

[LLFourn]

TxOdering::Shuffle is not shuffling the inputs (only the outputs).

Bug found while doing bdk core integration. I think it's moderately serious so I think this fix should be backported.

[nassersaazi]

i would love to work on this! it would be my first time contributing to the project, so some context around the issue is highly appreciated

[notmandatory]

Hi @nassersaazi thanks! but I didn't see your note and I just created #876 . Please feel free to review that PR, but it's very simple, the only interesting thing is to see if you can think of any other test cases or any reason why the tx inputs shouldn't be shuffled when we shuffle the outputs.