Add more tests and logic check the skipped_stats function

[MrPowers]

The skipped_stats function (and the filters_to_sql / filter_to_sql queries it rely on) should be better tested. There are probably corner cases / bugs in the function.

The function could also use a logic check from a pair of fresh eyes.

[brayanjuls]

@MrPowers - hey! I would like to work on this.

[MrPowers]

Awesome, thanks @brayanjuls

[brayanjuls]

@MrPowers - working on this issue I just realized we can do the same in delta scala using DeltaLog..snapshot.filesWithStatsForScan, after finishing with this I will take a deeper look at it.