[PACKAGE] Add libxs

[mtaillefumier]

This PR adds the libxs package.py written by @mkrack and update the cp2k package.py file accordingly

• Added libxs dependency
• Updated cp2k

[mtaillefumier]

@spackbot fix style

[spackbot-app]

Let me see if I can fix that for you!

[spackbot-app]

I was able to run spack style --fix for you!

spack style --fix

repos/spack_repo/builtin/packages/cp2k/package.py
repos/spack_repo/builtin/packages/libxs/package.py
�[1;34m==> �[0mrunning ruff format
2 files reformatted
�[1;34m==> �[0mrunning ruff check
�[1m�[91mF841 �[0m�[1mLocal variable `spec` is assigned to but never used�[0m
  �[1m�[94m-->�[0m repos/spack_repo/builtin/packages/libxs/package.py:42:9
   �[1m�[94m|�[0m
�[1m�[94m41 |�[0m     def cmake_args(self):
�[1m�[94m42 |�[0m         spec = self.spec
   �[1m�[94m|�[0m         �[1m�[91m^^^^�[0m
�[1m�[94m43 |�[0m         args = [
�[1m�[94m44 |�[0m             self.define_from_variant("LIBXS_FORTRAN", "fortran"),
   �[1m�[94m|�[0m
�[1m�[96mhelp�[0m: �[1mRemove assignment to unused variable `spec`�[0m

Found 2 errors (1 fixed, 1 remaining).
No fixes available (1 hidden fix can be enabled with the `--unsafe-fixes` option).

Keep in mind that I cannot fix your flake8 or mypy errors, so if you have any you'll need to fix them and update the pull request. If I was able to push to your branch, if you make further changes you will need to pull from your updated branch before pushing again.

I've updated the branch with style fixes.

[mtaillefumier]

@spackbot fix style

[spackbot-app]

Let me see if I can fix that for you!

[spackbot-app]

I was able to run spack style --fix for you!

spack style --fix

repos/spack_repo/builtin/packages/cp2k/package.py
repos/spack_repo/builtin/packages/libxs/package.py
�[1;34m==> �[0mrunning ruff format
2 files left unchanged
�[1;34m==> �[0mrunning ruff check
All checks passed!
�[1;34m==> �[0mstyle checks passed

Keep in mind that I cannot fix your flake8 or mypy errors, so if you have any you'll need to fix them and update the pull request. If I was able to push to your branch, if you make further changes you will need to pull from your updated branch before pushing again.

I wasn't able to make any further changes, but please see the message above for remaining issues you can fix locally!