Force 'cell' datasets in DqdvFitter to have 'Ah' column

[c-randall]

Description

The new DqdvFitter and downstream calc_lam_lli and plot_lam_lli functions required information about the full-cell maximum capacity. This was always planned to add, but was not done during the original overhaul of the dqdv module. Thus, without expert knowledge of the code it was challenging to use. Now, checks require the cell data of the fitter to always have an Ah column. This allows the fitter to store the max capacity and pass it along through fit results/tables, etc.

The DqdvFitter class also now provides a check to make sure the datasets are correctly oriented. That is, as SOC increases, the voltage decreases in the negative-electrode dataset, and increases in the positve-electrode and full-cell datasets. This reduces added stress on the user to guarantee this convention.

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that improves speed/readability/etc.)
• Bug fix (non-breaking change which fixes an issue)
• Chore (any other clean up, maintenance, etc.)

Key checklist:

• No style issues: $ nox -s linter [-- format]
• Code is free of misspellings: $ nox -s codespell [-- write]
• All tests pass: $ nox -s tests
• Badges are updated: $ nox -s badges

Further checks:

• The documentation builds: $ nox -s docs.
• Code is commented, particularly in hard-to-understand areas.
• Tests are added that prove fix is effective or that feature works.