Slightly optimize ApproximateBestSubset and its usage for PS txes (#3184)
Slightly optimize ApproximateBestSubset and its usage for PS txes (#3184)

* From 2 best sets with the same `nTotal` in ApproximateBestSubset prefer the one with less inputs

* There is no reason to run ApproximateBestSubset again if nMinChange is 0

* Apply review suggestions

ionomy/ion,ionomy/ion,ionomy/ion,ionomy/ion,ionomy/ion,ionomy/ion