For consideration: go back to just zarr

[psobolewskiPhD]

The most acute problems forcing #45 turned out to be napari internals issues that were masked by dask caching.
If we improve handling of non-dask-cached data in napari we might be able to go back to pure zarr here.
See also: napari/napari#8715
and napari/napari#8678

[psobolewskiPhD]

I'm mostly making this as a placeholder issue, because I don't think we're there yet. But we might get there!