Replace pygeodesics

[jo-mueller]

Description

This PR replaces the pygeodesics dependency with the potpourri3d and gdist packages, which will hopefully work fine on Mac and Python versions newer than 3.10.

The geodesic path calculation comes from potpourri3d, the distance matrix calulcation comes from gdist

Type of Change

• Replaces backend functionality

How Has This Been Tested?

• Unit tests
• Benchmark notebook on synthetic data

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes