MPI Extension for Julia >= 1.9 + Distributed support (Single node only)

[carstenbauer]

... so that we can implement pinthreads_mpi and pinthreads_distributed based on the actual rank / worker id information.

See #61. (Doesn't close it because in this PR we focus only on a single node.)

• [x] getcpuids_distributed docstring
• [ ] Distributed tests
• [x] MPI tests
• [ ] Add :cores option to pinthreads_hybrid
• [ ] Documentation