Investigate speed of multiple cartesian to spherical implementations

[subagonsouth]

Algorithm Description:

@lacoak21 reported that the implementation of geomotry.cartesian_to_spherical was slow. Her implementation in imap_processing/ultra/l1c/make_helio_index_maps.py::vector_ijk_to_theta_phi showed a speedup.

This ticket is to investigate and speed up the geometry module implementation if possible. Also, the speed of geometry.cartesian_to_latitudinal should be checked.