Add change to CML collateral logic

[MitchTurner]

WE currently just choose the smallest "valid" UTxO as our collateral. But according to this:
https://twitter.com/_KtorZ_/status/1598471789574856704?s=20&t=DFEkjQZKu-ajVvRMc2UB9w
we can use whichever UTxO and specify the right amount of change. That's much more robust.

[MitchTurner]

Oh. This is just a V2 feature. So we just need to make sure we include this in our V2 impl here:
#40