Add TokaMaker geometry interface

[fs2819]

This PR adds the ability to pass geometry information from TokaMaker directly (i.e. in memory) to TORAX via the 'tokamaker' geometry mode. The geometry information is calculated by TokaMaker (using the new get_fsa() function) and then passed to TORAX as a dict of arrays.

This geometry mode bypasses the saving and reading of eqdsk files, which is especially useful for the TokaMaker+TORAX pulse design workflow (which currently requires saving and loading hundreds of eqdsk files).

This does not add a dependency for TokaMaker (or OFT) to TORAX. The geometry inputs are simply floats and NumPy arrays. The new tokamaker_test.py added for this geometry type creates TokaMaker-like dict of arrays from a dummy cylindrical geometry, not requiring TokaMaker.