Hash based reproducible and expandable stratified splitting

[wli51]

I think this works, but you could also use hash splitting, which would ensure samples remain in their respective splits even if data is added or removed (such as with QC). Here is an example if interested:
https://github.com/WayScience/nuclear_speckles_analysis/blob/main/splitters/HashSplitter.py

Originally posted by @MattsonCam in #29 (comment)