Use scipy distance_transform_edt to replace slow loop

[trhille]

Use scipy distance_transform_edt to replace slow loop, speeding up get_dist_to_edge_and_gl by orders of magnitude.

Checklist

• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[trhille]

Testing

Testing on 8–30km Antarctica mesh.
With these changes: compass.landice.mesh.get_dist_to_edge_and_gl() took 0.05 seconds
With previous: compass.landice.mesh.get_dist_to_edge_and_gl() took 57.52 seconds

The resulting meshes differ by a few cells, so I can't directly difference them. Visually, they are very similar but not identical. Left is using main, right is using these changes:

I've saved out the arrays dist_to_edge and dist_to_grounding_line in each branch. RMSE and MAE for dist_to_edge are 0.0012467 and 0.00038777, respectively. For dist_to_grounding_line, RMSE and MAE are 0.00077373 and 0.0001492. For reference, distances range up to 200000.

[trhille]

After rebasing onto main to include changes from #935, differences are still small, with MAE of 0.00038777 and 0.00034768 and RMSE of 0.0012467 and 0.0011817 for dist_to_edge and dist_to_grounding_line, respectively. Cell spacing looks slightly different from before #935 was merged, but still very similar to each other.