We should convert to ZARR?

[vreuter]

The project currently uses CZI as its input, but it'd be more flexible to add a generic ZARR conversion step and then work with ZARRs from there on.

[vreuter]

Quick test on data from @ines-prlesi suggests that pylibczi is quite fast, so at least for CZI-stored image data, staying in that format may be desirable.