add elastic tensor voigt form check and conversion if needed

[joehart2001]

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Summary

For some models, matcalc returns the tensor as a plain 
numpy.ndarray with shape (3, 3, 3, 3), not as a pymatgen 
tensor object. NumPy arrays do not have .voigt, so the 
final dataframe conversion fails -> we need to be robust to this

@Fraser-Birks i can't add you as a reviewer but would be good to scan over, thanks!

Linked issue

Resolves #

Testing

ran elas benchmark