add bidcell subworkflow

[an-altosian]

The first draft of the bidcell workflow proposed in #17

[an-altosian]

The python script, module, and subworkflow is basically done. I have tested it using the latest version of xenium bundle.

Caveats:

1. BIDCell has to run with GPU, so we might need to add some prechecks to ensure GPU is accessible.
2. It uses DAPI focused image (morphology_mip.ome.tif or morphology_focus/morphology_focus_0000.ome.tif) instead of the Z-stack one (morphology.ome.tif).
3. It takes a single channel containing both the bundle and the ref as the input. It output the entire output folder. I will adjust this once know more about what the downstream modules take.
4. If no ref is provided, it will use a dummy ref provided in BIDCell github repo and set the weight of positive and negative markers as zero.
5. If no elongated cell types are provided, it will add a dummy one called placeholder to the ref because otherwise BIDCell complains.

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