Remove PhaseSpecies from configuration and extend Species to support phase-specific properties

[boulderdaze]

PhaseSpecies is not intuitive for users. It requires users to maintain separate Species and PhaseSpecies objects. PhaseSpecies exisits to provide phase-dependent properties such as diffusion coefficients and density.

Species properties can be accessed through the C API's GetProperties() template function, while PhaseSpecies does not have equivalent support. In the downstream APIs (Python and Fortran), phase-specific properties currently appear to be ignored, but this requires further investigation. (Related issue: NCAR/musica#938)

• Remove the PhaseSpecies
• Extend Species to support phase-specific properties, including diffusion coefficient and density.
• Provide backward compatibility guidance for users currently using PhaseSpecies.

[boulderdaze]

Hi @mattldawson, Kyle and I discussed some issues with PhaseSpecies struct based on user feedback and our current implementation, which doesn't support reading the properties yet. Since your latest musica PR touches the phase species in python, I thought it'd be worth tagging you to get your thoughts on this.

[K20shores]

Summary of our meeting

Leave PhaseSpecies alone for now. Just update the python/javascript/julia APIs in musica to add a .add API to phases which takes in a species and properties for that species which removes the need for users to ever use a PhaseSpecies object directly