Consider updating k coefficients in pvlib.pvarray.huld

[kandersolar]

The EU JRC has published updated coefficients for what we call the huld model: https://doi.org/10.1002/pip.3926

We could update the coefficient values currently available in pvlib.pvarray.huld, or add these as new ones.

The paper also briefly describes the fitting procedure they used, although I'm not sure it's detailed enough to change the situation with #1979.