Follow-up to #1363 (update from spack dev 20241031): set correct mpiifx/mpiifort in MPI meta module, update Intel MPI in site configs

[climbfuji]

Summary

1. For all site configs that use the Intel classic compilers with Intel's MPI (intel-oneapi-mpi%intel), set variant +classic-names in the external package definition - this makes spack use icc, icpc, ifort. For intel-oneapi-mpi%oneapi (icx, icpx, ifortorifx`), this isn't needed.
2. Add CI workflow on Ubuntu with icx, icpx, ifx. At some point later, the mixed setup icx, icpx, ifort will go away, but for now, we need both.
3. Update setup-meta-modules extension: save the compiler config from the preferred compiler (last entry in the list of compilers) so that it is available for creating the MPI meta module. This is needed so that we can set the correct MPI compiler wrapper commands (e.g. mpicc vs. mpiicc vs. mpiicx).

Testing

• Locally on my laptop with %oneapi (icx, icpx, ifx)
• CI (checked that all Ubuntu CI runs had the correct MPI compiler wrappers in the MPI meta modules for the given compiler)

Applications affected

None

Systems affected

None really

Dependencies

n/a

Issue(s) addressed

Working towards #912

Checklist

• This PR addresses one issue/problem/enhancement, or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.