feat: Galax to Gala io

[nstarman]

• First use case for as_interop (Galax Feature Parity #298)
• Major cleanup of I/O.
• consolidate a lot of private API.
• Better docs: 1. plum.dispatch combines the docs for IDEs, 2. we can show round-tripping of the potential.
• Access to galpy via galax -> gala -> galpy!

[codecov]

Codecov Report

Attention: Patch coverage is 86.17886% with 34 lines in your changes missing coverage. Please review.

Project coverage is 94.31%. Comparing base (ffb7f56) to head (8f3b7c8).

Files	Patch %	Lines
src/galax/_galax_interop_gala/potential.py	86.12%	34 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #375      +/-   ##
==========================================
- Coverage   94.81%   94.31%   -0.50%     
==========================================
  Files          69       69              
  Lines        2449     2621     +172     
==========================================
+ Hits         2322     2472     +150     
- Misses        127      149      +22     

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[nstarman]

Gonna add more docstrings (which are also tests). Then all the available conversions should be fully documented.
A good followup PR would be to allow a time argument when converting from galaxy to gala /galpy
Edit: done! Every conversion function has an example. These are all doctested.

[nstarman]

Potentials requiring GSL remain untested (#278)

[nstarman]

Ping @adrn, does this look good to you?

[nstarman]

I'm going to branch this PR to get started on the galax <-> galpy I/O.