test_ogrsf: add -threads and -loops options

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26311 f0d54148-0727-0410-94bb-9a71ac55c965
Fix thread-safety of swq_op_registrar::GetOperator() (#5196)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26312 f0d54148-0727-0410-94bb-9a71ac55c965