WFS: optimize WFS 1.0 (or WFS 1.1.0 where RESULTTYPE=HITS isn't available) so that in some circumstances the GML stream downloaded is used to compute GetFeatureCount() and GetExtent() together

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25517 f0d54148-0727-0410-94bb-9a71ac55c965