Add distributed CellPose segmentation

[krokicki]

There are some implementations for distributed CellPose, e.g.
MouseLand/cellpose#244
MouseLand/cellpose#408

We need to implement one of these into the pipeline as an alternative segmentation method, just like Airlocalize and RS-FISH are implemented. We'll add a parameter --use_cellpose that will be a boolean option, for now disabled by default.