Improve handling of napari viewer events in prediction

I think changing the way this is handled would require a fair bit of work, probably better for another PR. Will make an issue for it

_Originally posted by @saeliddp in https://github.com/AllenCell/allencell-ml-segmenter/pull/196#discussion_r1520533839_

Right now, if anything happens in the napari viewer, our existing checkboxes are destroyed and repopulated. This is necessary for now because we need the order of the checkboxes to align with the order of images in the viewer; would be nice if we could do this in a way that does not require that alignment. (this way, existing checked boxes would persist)