FindEXPAT: add a EXPAT_USE_STATIC_LIBS hint
The effect of that hint is to restrict the candidate library names, but more essentially to set the XML_STATIC compile definitions which is required to get proper linking (cf https://github.com/microsoft/vcpkg/issues/1100 and https://github.com/OSGeo/gdal/issues/7955)
Topic-rename: FindEXPAT-static
Edited by Brad King