[enhancement] Maltsev prescription

[ezapartas]

Implementing Maltsev explodablity criterion:

As an alternative to Patton20+Ertl16 criterion, now we have Patton20+Maltsev25 criterion

For now, implementation only for M_CO <= 10 Msun (as in Patton20+Ertl16 criterion). Still needed to implement the case for M_CO > 10 Msun (where the MT history is needed right now).

To work it still needs:

• to include the Kepler_sc.dat table as in the POSYDON data of Patton, so that it is able to be read.
• to make new SN MODELS based on this prescription for initial-final interpolation

[dimsour94]

I ran a population of 5,000 systems using this branch, including the Maltsev central entropy file with nearest-neighbour and interp_values set to False, and it worked well. The only remaining open issue is the treatment of SNe forming fallback BHs: we currently assume a fallback fraction of 0.99, but we still need to determine what the appropriate fallback fraction should be.

[sgossage]

@ezapartas @dimsour94 is this ready for review?

In principle, things look good outside of the TODO points raised in the PR's description. The current v2.3 branch also needs to be merged in to this.

[maxbriel]

I've updated this PR with the unaddressed comments:

• Merger v2.3 into this branch
• I fixed the setting of f_fb and state in the case conserve_hydrogen==True.
• I made sure the k1 and k2 parameters in explod_crit are passed into it from the main function, instead of redefining them. Additionally, there was a typo in the k2 parameter (0.421 instead of 0.420).
• Changed to self.RNG instead of random.
• Some additional cleanup of comments and indentations.

One problem I am seeing with this PR is the backwards compatibility. It forces the user to always have the new Kepler_sc_table.dat file in their PATH_TO_POSYDON_DATA, even if they are not using the Matlsev prescription.
Do we want this?

Next steps:

1. Add Kepler_sc_table.dat to POSYDON_auxilliary_data.
2. Post-process grids for new SN_models to be included and retrain the interpolators