Prism cython

[jcapriot]

Updates the prism functions to use cython instead of C... two reasons:

1. The compiled prism functions are still numpy ufuncs, but writing them in cython will make it much easier for someone besides myself to digest.
2. Writing them in cython allows us to do some fancy magic to get them to work simultaneously with numba.njit!

In this PR I've registered them so that numba should know what to do with them.

[codecov]

Codecov Report

Merging #67 (3cf25a7) into main (5408065) will increase coverage by 0.00%.
The diff coverage is 87.50%.

@@           Coverage Diff           @@
##             main      #67   +/-   ##
=======================================
  Coverage   87.47%   87.47%           
=======================================
  Files          29       30    +1     
  Lines        3043     3067   +24     
=======================================
+ Hits         2662     2683   +21     
- Misses        381      384    +3     

Files	Coverage Δ
geoana/kernels/_extensions/__init__.py	87.50% <87.50%> (ø)