Equinox modules

[tbmiller-astro]

A few backend things are added in this PR

1. The main update is that priors and renderers are now equinox modules, which play much nicer with Jax things and should give us more flexibility going forward. This was done to try and help compile times, which it might have? but still a good thing to do.
2. sersic_pointsource profile added which, as the name suggests, just adds an additional point source element at the center of a sersic profile
3. Update Interpolation scheme for gaussian weights as a function of index in the Fourier and Hybrid renderers. Now uses a cubic spline with the interpax package instead of the polynomial fit to log(n). Should be more numerically stable and accurate.
4. Updated the docs with some api changes since the initial release.