OBJ: fix import of files with really large polygons (e.g. 7000 vertices in one poly)

Bug report #110948: a file with a polygon so large that a single line
is 140 kilobytes. The previous limit was 64kb, increase the read file
chunk limit to 256kb. Still not fully robust, would need a more
complex fix to support arbitrarily large line length limits.

source/blender/io/wavefront_obj/importer/obj_import_file_reader.cc

@@ -433,7 +433,7 @@ static void geom_new_object(const char *p,
       r_curr_geom, GEOM_MESH, StringRef(p, end).trim(), r_all_geometries);
 }
 
-OBJParser::OBJParser(const OBJImportParams &import_params, size_t read_buffer_size = 64 * 1024)
+OBJParser::OBJParser(const OBJImportParams &import_params, size_t read_buffer_size)
     : import_params_(import_params), read_buffer_size_(read_buffer_size)
 {
   obj_file_ = BLI_fopen(import_params_.filepath, "rb");

source/blender/io/wavefront_obj/importer/obj_importer.hh

@@ -20,6 +20,6 @@ void importer_main(Main *bmain,
                    Scene *scene,
                    ViewLayer *view_layer,
                    const OBJImportParams &import_params,
-                   size_t read_buffer_size = 64 * 1024);
+                   size_t read_buffer_size = 256 * 1024);
 
 }  // namespace blender::io::obj