romio: remove it

[hppritcha]

The MPICH project no longer supports a self-standing ROMIO library.

The embedded ROMIO does not support MPI 4 embiggening (MPI_Count). The embedded ROMIO cannot be built against modern versions of Intel's OneAPI API (ZE). The Open MPI I/O framework work has preferred the OMPIO component since v4.1.0 release.

So, we remove the ROMIO I/O component and remove ROMIO from the 3rd-party software. Update the MPI I/O documentation to no longer refer to ROMIO.

Various updates to github actions, etc.

[edgargabriel]

Looks mostly good to me, but because of the size of the commit, there is a good chance that I did not catch everything.

Just as a side note to the comment, OMPIO became the default component for all file systems starting ompi 4.1.x, not 5.0.x

[jsquyres]

Is it possible to add an MCA synonym for romio to be ompio? I.e., if someone runs mpirun --mca io romio, it would automatically substitute in ompio so that an IO module would be loaded and the job would still run?

I don't know if we do MCA param synonyms early enough for this to work, though.

[edgargabriel]

@jsquyres I am not sure I like this idea, this would make managing end-user expectations difficult, as well as potentially complicate bug reports. I would prefer that their script just fails and they have to make a one-time adjustment to the script. This is a different situation than vader/sm.

In addition, I am also not sure whether it could have legal ramifications.

[edgargabriel]

we removed for example btl/openib and osc/pt2pt from 4.1 to 5.0, and we just expected that users adjust their scripts. I don't think this is thaaat different.

[jsquyres]

@edgargabriel Ok, fair points.

[ggouaillardet]

FWIW, the current MCA param would be --mca romio314 or whatever ROMIO version we are using.

So I think end users are either used to adjusting their scripts, or they use --mca ^ompio (and I guess that would fail even with a synomym)

[hppritcha]

okay so are we ready to merge this?

[jsquyres]

In general, I think it's ready to go.

I should have thought of this before, though -- this one is important enough that we should put it in the release notes.

[hppritcha]

done added a blurb to the release notes for v6.0.x.
@jsquyres please check now.