[ci] Update Clang and GCC compiler version

[gruenich]

Ubuntu-latest does no longer support these old compilers

[gruenich]

• Upload fails for all builds.
• Some builds have failing AVX2 tests.
• Would be great to have Add icpx to CI #292 rebased and adapted to replace icpc by icpx.

[gruenich]

@bernhardmgruber I think this can be merged. It does not fix the pipelines, but makes them a bit more usable.

[Axel-Naumann]

Hi @gruenich could you reach out to me at axel@cern.ch please, if possible describing your use case for VC?

[bernhardmgruber]

@bernhardmgruber I think this can be merged. It does not fix the pipelines, but makes them a bit more usable.

Hi! I have moved on from CERN and maintaining Vc. I seem to still have some rights on the repository, but would kindly ask to discuss your change requests with @Axel-Naumann as he suggested above.

Please also notice that std::simd, the successor of Vc, has been approved for C++26. GCC 16 will have a partial implementation. @mattkretz also has his own implementation for GCC here: https://github.com/GSI-HPC/simd. This may help you transitioning away from Vc.

[gruenich]

Any reason to not merge this? Currently the CI testing is broken because the compiler no longer are part of Ubuntu-latest. After merging, this is going to be fixed. Just the failures with AVX2 remain.