Feature/positions analysis simplify

[Jammy2211]

Recent updates by Rich enable point-source modeling to now work correctly in autolens.

This required the implementation of a Point Solver, which determines the multiple images of a strong lens by ray tracing triangles to the source-plane and tracking which regions of the image plane contain the point source. This solver is now tested and works well, and also supports JAX.

This PR updates the fitting functionality associated with point sources, including:

• Supporting different image-plane chi-squared calculations (e.g. nearest pairs with and without repeats, an all-to-all scheme).
• Source plane chi squared based on the separation of the observed images in the source-plane.

All new features are described in the autolens_workspace.