Allow extending tests for any modules, regardless of existing ones in another entry of the `upgrade-path`. Bonus point: tests no longer need to be imported in the `__init__.py` file. closes odoo/odoo#121453 X-original-commit: ed1b27dbdfc0a5084051c59da9c4578262b3bf8c Signed-off-by: Christophe Simonis <chs@odoo.com> Co-authored-by: Alvaro Fuentes <afu@odoo.com>