### Body

Add unit test for changes in https://github.com/apache/airflow/pull/17305

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
tests/jobs/test_backfill_job.py
dag_id = 'test_job_id_is_assigned_to_dag_run'
        with dag_maker(dag_id=dag_id, start_date=DEFAULT_DATE, schedule_interval='@daily') as dag:
            DummyOperator(task_id="dummy_task", dag=dag)
        job = BackfillJob(
            dag=dag, executor=MockExecutor(), start_date=datetime.datetime.now() - datetime.timedelta(days=1)
        )
        job.run()
        dr: DagRun = dag.get_last_dagrun()
        assert dr.creating_job_id == job.id
    def test_backfill_has_job_id(self):
        """Make sure that backfill jobs are assigned job_ids."""
        dag = self.dagbag.get_dag("test_start_date_scheduling")
        dag.clear()
        executor = MockExecutor(parallelism=16)
        job = BackfillJob(
            executor=executor,
            dag=dag,
            start_date=DEFAULT_DATE,
            end_date=DEFAULT_DATE + datetime.timedelta(days=1),
            run_backwards=True,
        )
        job.run()
        assert executor.job_id is not None