CI: Add compile-only coverage for more conduits

[bonachea]

Summary

As previously discussed, this PR expands compile-time coverage in CI to include:

• ibv, ucx, ofi and mpi on Linux
• ofi and mpi on macOS

Currently most jobs are relying on an OpenMPI package for mpi, which in most cases means MPI_CC is backed by an OS-dependent compiler (which in general will differ $CC). However the current combinations all appear to be link-compatible and we're not running execution-time tests anyhow. The icx configs instead use Intel MPI (with the matching CC) that was already preinstalled in the container.

Rough Job Performance Impact

Ubuntu jobs that previously would complete in 2.0..4.5 minutes now complete in 4.0..7.5 minutes
macOS jobs that previously would complete in 4.0..15.0 minutes now complete in 4.0..15.0 minutes

So Ubuntu jobs have gotten roughly 2-3 minutes longer.
macOS jobs have also gotten longer on average, but the "long tail" is still under 15 minutes.
In both cases, most of the slowdown is coming from the make all and make check steps (which are now doing 2x or 3x more compilation and linking than before). But that's exactly where we're seeking to add coverage.

[PHHargrove]

LGTM with one minor exception:

One of the commits removes the following line w/o explanation:

extra_flags: -g -mmlir -allow-assumed-rank

Assuming that was intended, please either update the commit message to explain its removal, or (if feeling pedantic, which I am NOT) split it out to a distinct commit (which can stay within this PR).

[bonachea]

One of the commits removes the following line w/o explanation:

extra_flags: -g -mmlir -allow-assumed-rank

Assuming that was intended, please either update the commit message to explain its removal, or (if feeling pedantic, which I am NOT) split it out to a distinct commit (which can stay within this PR).

Yes it was deliberate, -mmlir -allow-assumed-rank only matters for Fortran code.
This was copy-pasta accidentally preserved from the Fortran template used to create the YML.

I've updated the commit message as requested.