New test setup runs only minimal tests on macOS

[heplesser]

The new test setup created in #2590 only performs minimal checks under macOS, as it is built without support for MPI, OpenMP, GSL, Python (see https://github.com/nest/nest-simulator/actions/runs/4858443145/jobs/8659888539#step:8:11, https://github.com/nest/nest-simulator/actions/runs/4858443145/jobs/8659888539#step:12:295). It should run the full set of tests except those requiring sionlib, music, libneurosim.

See also #2660 for fixes to the old CI setup that allowed running test with OpenMP again under macOS. The crucial point was to inform Cmake about the location of the OpenMP library installed by Homebrew:

CONFIGURE_OPENMP="${CONFIGURE_OPENMP} -DOpenMP_ROOT=`brew --prefix libomp`"

I'd create a PR myself but feel a bit uncertain about the new setup, so I create this issue.