FindHDF5: Restore pre-3.6 behavior of finding only C by default

Refactoring in commit v3.6.0-rc1~72^2 (HDF5: Rework component searching
to correctly find HL for all bindings, 2016-05-12) changed the default
behavior from finding only the C bindings to finding everything for the
enabled languages.  Restore the original behavior for compatibility and
because many projects need only the C bindings.

Closes: #16397