Replace iterrows with apply for linking organoids to single cells

[MikeLippincott]

There might be an opportunity to collapse the loops here by using the single-cells as the focus and leveraging an apply; consider checking each single cell for each organoid within a function where the function takes as input the record columns and checks against all organoid bboxes. Apply tends to be more performant than iterrows so you might gain some performance here too.

Originally posted by @d33bs in #59 (comment)