Produce cell mask polygons and connect to bento-tools for post-hoc geometrical assessment

[EliHei2]

Bento-tools by @ckmah, would be a perfect add-on to segger. It will be beneficial to add it to the validation module. I could thought of the following steps.

• [x] Produce polygon cell masks. This is assigned to @rukhovich
• [ ] Connect to SpatialData as the backbone of bento. @LucaMarconato
• [ ] Connect bento to segger. @ckmah

pinging @andrewmoorman too. let me know if I missed a step.