Tests: Extend FindHDF5 tests to link and run executables

Brad Kingrequested to merge
brad.king/cmake:ci-FindHDF5 into master

Verify that this works using both targets and variables.

In Fedora's HDF5 packages for OpenMPI and MPICH, the h5pfc compiler wrappers for Fortran use the wrong search path for their Fortran modules. Patch them locally in CI jobs until it is fixed in Fedora upstream.

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