FindHDF5: port modern CMake target construction from VTK
The latest HDF5 versions still allow installation from autoconf files rather than the CMake-based installation, but guaranteeing a modern HDF5 target would be a boon to modern CMake projects.
I've imported @ben.boeckel's changes to FindHDF5 from VTK (see !2575 (closed), #18560 (closed)). It removes the "library type detection" from VTK but is otherwise unchanged.