geospace-code/h5fortran: bugfix: internal intent(inout) for read

Fortran intent(out) arguments reallocate allocatable variables, even if they were already allocated. This can cause segfaults on large variables (gigabyte or so), so we change internally to intent(inout). No user program changes are required. This issue affects any Fortran program in general.

• HDF5 autobuild requires CMake >= 3.20. It's generally easy to install a recent CMake, and the performance for auto-building is much better as a result.

• FindHDF5 is enhanced to work with HDF5 library linked with MPI. We don't yet include parallel HDF5 features, but it's being prototyped in a separate repo.