Bring over Fortran MPI_Status conversion function fixes to v4.1.x

[jsquyres]

Bring over #7762 and #8043 to the v4.1 branch.

I marked this as "minor" because although technically it's a bug in MPI conformance, this bug has been un-noticed -- for years -- in both Open MPI and MPICH. So it's definitely not too important.

But OTOH, it should be simple cherry-picks from master to v4.1.x. Hopefully, it's easy to do.

[jsquyres]

@ggouaillardet Do you have a little time to try to do this, perchance?

[ggouaillardet]

This is simple if we first cherry-pick 98bc7af (change the definition of type(MPI_Status) in use-mpi-f08).

I cannot remember what we decided about that

• this breaks ABI, so no backport
• the code is broken, so breaking ABI is a lesser evil here

If we choose not to backport the type definition change, we would have reimplement the conversion subroutine
(no more memcpy() ...). That's not rocket science, but a bit time consuming.

can you please advise on how you want to move forward?
(I should be able to find some time next week)

[jsquyres]

Excellent point -- I forgot about the ABI-breaking stuff. Thanks for the reminder.

Let's not bring this over to v4.1.x, then. We only found this bug by an internal audit, not a real MPI code -- this is pretty low priority. We'll let it all be fixed in v5.0.