Documentation: run-time changes v4.1.x --> v5.0.x

[jsquyres]

Originally taken from the "to-do" section in the Open MPI docs:

• [ ] man-openmpi/man1/mpirun.1.rst is currently essentially an RST-ified version of OMPI v4.1’s mpirun(1) man page. There has been some light editing:
  • Eliminiated all -foo options
  • Modernized some of the examples
  • Much more work needs to be done to update it for all the PRTE changes since Open MPI v4.1.x.
• [ ] Document this new breakpoint functionality: https://github.com/open-mpi/ompi/commit/f97d081cf9b540c5a79e00aecee17b25e8c123ad
• [ ] Add that we do support “single dash” mpirun options, but we don’t want people to do that.
• [ ] This is not really a change in v5.0, but it probably has changed (because of PRTE) since v4.x, so: we need to document how to use MPI_Comm_join and MPI_Publish_name + MPI_Comm_accept / MPI_Lookup_name + MPI_Comm_connect.
  • See https://github.com/open-mpi/ompi/issues/10222
• [ ] Add a section about debugging and removal of MPIR, yadda yadda yadda (at least some of this can come from the “parallel debugging” FAQ section).
• [ ] https://github.com/open-mpi/ompi/issues/7668 (ORTE –> PRRTE user-visible changes)
• [ ] Add docs about mpirun launch vs. direct launch.
• [ ] From Josh Hursey:
  • This is an old link to section 10.8.21 -- it may or may not be correct https://ompi–8329.org.readthedocs.build/en/8329/faq/running-mpi-apps.html
  • Is "aggressive" mode really determined by the slot count provided by PRRTE? Or is it determined by a query to hwloc with a reference to the number of processes per node. It just surprises me that this part of OMPI is controlled by PRRTE instead of something more generic that might work with, say, Slurm direct launch via srun.