Draft: Resolve "fix mendeleev elements.py has been removed"

Closes #4312

see module changes https://github.com/lmmentel/mendeleev/pull/121/files

This MR tries to fix the issue with mendeleev.elements module that has been removed in v0.16.0

Also, in 0.16.0 they try to avoid loading all the elements and make the access lazy (see 'Defer loading element data until attribute access '). In bliss.physics.diffraction it was also loading all crystals at once, so this MR tries to make it lazy too.