Add GPU and batch size support to Cellpose

[andrewmoorman]

Adds support for GPU usage and batch size configuration:

• Adds use_gpu and batch_size parameters to CellposeSegProperties and CellposeSegParameters.
• Passes these parameters to Cellpose and CellposeModel constructors in predict.py.
• Maintains default behavior (use_gpu=False and batch_size=8) for compatibility.

✅ Linted with flake8
✅ Based on develop
✅ Tests still have >90% coverage (just added input parameters)
✅ Tested with the run-segmentation CLI command in vizgen-postprocessing using use_gpu=True and batch_size=96

Let me know if anything should be adjusted!