Use CellCanvas with multiple tomograms

[kephale]

There are 2 aspects of this, one is easier than the other:

1. Train a model on multiple tomograms
2. Apply a model to multiple tomograms

(2) is kinda addressed by things like https://github.com/cellcanvas/cellcanvas/issues/9#issuecomment-1973339045

However, (1) has some design/UI challenges because we currently are fairly tightly linked to just working on 1 tomogram at a time. Flagging @kandarpksk @Janeece

Both were requested by David Agard