Optimize loading meshes using numpy arrays

1) avoid calling geometry.xxx multiple times as each time it creates a new copy
2) use numpy arrays with correct data type, so Blender could perform buffer copy significantly reducing overhead

src/bonsai/test/tool/test_model.py

@@ -614,7 +614,7 @@ class TestApplyIfcMaterialChanges(NewFile):
         tool.Geometry._reload_representation(obj)
 
         def get_material_indices(mesh: bpy.types.Mesh) -> np.ndarray:
-            buffer = np.empty(len(mesh.polygons), dtype=np.int32)
+            buffer = np.empty(len(mesh.polygons), dtype="I")
             mesh.polygons.foreach_get("material_index", buffer)
             return buffer