ci(compilers): ci test with ifx, trim compiler compat test matrix

[wpbonelli]

Start testing with ifx 2024.1 in CI. No prior ifx version can build mf6 and pass tests. I haven't yet checked 2024.2 as it still needs support in fortran-lang/setup-fortran.

There are a few tests failing in output equality comparisons — will need to see if these can be remedied with compiler precision/optimization flags or if the comparisons need relaxing.

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