net/py-mpi4py: Update 3.1.6 → 4.0.0

Backward-incompatible changes:

• Python 2 is no longer supported, Python 3.6+ is required, but typing stubs are supported for Python 3.8+.
• The Intracomm.Create_group() method is no longer defined in the base Comm class.
• Group.Compare() and Comm.Compare() are no longer class methods but instance methods. Existing codes using the former class methods are expected to continue working.
• Group.Translate_ranks() is no longer a class method but an instance method. Existing codes using the former class method are expected to continue working.
• The LB and UB datatypes are no longer available, use Datatype.Create_resized() instead.
• The HOST predefined attribute key is no longer available.
• The MPI.memory class has been renamed to MPI.buffer. The old name is still available as an alias to the new name.
• The mpi4py.dl module is no longer available.
• The mpi4py.get_config function returns an empty dictionary.

Changelog:
https://github.com/mpi4py/mpi4py/releases/tag/4.0.0

Exp-run looks fine.

Take maintainership.

PR: 280883