Updated critical curve and caustic functions

[kassidy-kollmann]

I made changes to the following functions in autogalaxy/operate/deflections.py:

• tangential_critical_curve_from and radial_critical_curve_from: I updated these two functions so that they now return all tangential (and radial) critical curves for the lensing system, as opposed to returning only one curve even when multiple exist. With these changes, the critical_curves_from function still returns a list with two entries, however, now each entry is its own list containing all tangential critical curves (for the first entry) and all radial critical curves (for the second entry).
• tangential_caustic_from and radial_caustic_from: These functions now return all tangential (and radial) caustics. The caustics_from function now returns a list with two entries, where the first entry is a list of all tangential caustics and the second entry is a list of all radial caustics.
• area_within_tangential_critical_curve_from, einstein_radius_from, einstein_mass_angular_from: Since there may be multiple tangential critical curves for a lensing system, these functions now return lists where each entry corresponds to one tangential critical curve.

[Jammy2211]

I have made the following updates and will now merge to main:

• Updated the API of deflections.py to explicitly name functions to return a list (e.g. tangential_critical_curve_list_from.
• Removed all instances where tangential and radial critical curves / caustics are merged into one (e.g. in the plotting functions), such that one can separately customize them. This includes removing critical_curves_from / caustics_from.

Thank you!