Treatment for spglib v2.5.0 DeprecationWarning

[atztogo]

From spglib v2.5.0, spglib.get_symmetry_dataset() and spglib.get_spacegroup_type() return kinds of dataclass, and dot access instead of dict key is recommended. Therefore, the dict access emits DeprecationWarning.

https://spglib.readthedocs.io/en/stable/api/python-api/spglib/spglib.html#spglib.SpglibDataset
https://spglib.readthedocs.io/en/stable/api/python-api/spglib/spglib.html#spglib.SpaceGroupType

This PR is to prevent it. I added a function get_dot_access_dataset, which mimics dot access for those dictionary for spglib < v2.5.0.

[atztogo]

@giovannipizzi, probably you are super busy. Do you know anybody who can review this PR?

[giovannipizzi]

Thanks @atztogo for taking care of this, and for pinging me! (I don't look at all GitHub notifications, just too many...)
Changes look fine and tests pass, so I'm merging this. I didn't check if more changes are needed, but I guess you checked there are no other instances?

Also, I imagine you need a pypi release, right? Let me know and I will prepare one

[atztogo]

I guess you checked there are no other instances?

I hope so.

I imagine you need a pypi release, right?

Yes, but I can take care of it if you want. Quite a few people rely on seekpath via pypi and conda forge.