Three component phase separation for ultramassive white dwarfs, part 2

[evbauer]

Updated code in phase_separation.f90 and a new wd_o_ne_3_phase test suite.

[evbauer]

@mcastrotapia I've pushed a few "housekeeping" fixes to get the static analysis script to pass, so you might want to merge this branch into your fork to stay up to date.

Anyway, this PR will eventually be the one that merges the code into main once I get a chance to review the substance of the code. So I'll either leave comments/questions here for you or push changes directly on this branch. If you end up needing to push substantial code updates, you can open a new PR onto this three_component_PS branch, and then if we merge them those changes will eventually make their way into MESA main via this PR.

Thanks for submitting this code!

[mcastrotapia]

Thanks for the fixes and for reviewing the PR! I will merge the branch into my fork, and I'll be attentive to comments/questions and updates.