Add CrI3 tutorial (spin-polarised kcp calculation)

[nscolonna]

• np.max does not work with lists of list with different shape. Fixed
• The function to get the number of spin channel was not implemented correctly in the UI calculator
• Add a tutorial on how to run nspin=2 calculations for extended systems with KCP (tutorial_6: ferromagnetic CrI3 semiconductor)

[pep8speaks]

Hello @nscolonna! Thanks for updating this PR.

• In the file tests/helpers/patches/_benchmark.py:

Line 115:121: E501 line too long (124 > 120 characters)

• In the file tests/helpers/patches/_mock.py:

Line 162:121: E501 line too long (255 > 120 characters)
Line 174:121: E501 line too long (221 > 120 characters)

Comment last updated at 2024-10-11 13:45:17 UTC

[nscolonna]

Apparently setting the locale to en_US.UTF8 or es_US.utf8 works on my machine but not on the one the CI tests are run.
Do not know how to solve this ...
Otherwise this PR is ready to be reviewed and merged

[elinscott]

@nscolonna I have brought this PR up-to-date with master. The bugfix that the original PR sought to solve was actually fixed by #220 but this PR still adds the CrI3 tutorial so we still want to merge it. I have changed the title accordingly.

[nscolonna]

Thanks! sounds good!