Avoid using old input-fermi.dat files

[kavanase]

I've mentioned this before, but noting here as it's come up again. The approach of having to create an input-fermi.dat file to then run a SC-Fermi process internally in TLC is:

• A significant burden on the user to create this file, which has a unique format not used elsewhere, particularly for lower symmetry systems with many defects.
• Confusing, as some users have expected they only needed to input the recombination-active defects to this (I will add a note to clarify this) which can give nonsense/inaccurate results.
• Possibly inaccurate in a lot of cases, due to poor numerical convergence, improper degeneracy handling, fixed defect grouping, non-customisable with other thermodynamic constraints (e.g. T-dependent gap/chemical potentials, fixed impurity concentrations...), no site competition for high concentration defects etc, all of which are handled in doped's thermodynamics methods.
• Slower
• Prevents easy looping over different conditions, as in e.g. Wang et al. Joule 2024 Fig 5

It would be much better if the user could provide known defect concentrations / sc Fermi level (e.g. from doped or otherwise) to avoid this step and its associated issues. And/or, if a doped DefectThermodynamics object could be provided, which has all the required info readily available in simple convenience methods to (optionally) replace this part of the code