GitLab

Make it possible to proceed to a regular lookup in locals_dict if the
custom type->attr fails.  This allows type->attr to extend rather than
completely replace the lookup in locals_dict.

This is useful for custom builtin classes that have mostly regular methods
but just a few special attributes/properties.  This way, type->attr needs
to deal with the special cases only and the default lookup will be used for
generic methods.
Signed-off-by: Laurens Valk <laurens@pybricks.com>