### 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.
airflow/jobs/backfill_job.py
self,
        ti_status,
        executor,
        pickle_id,
        start_date=None,
        session=None,
    ):
        """
        Process a set of task instances from a set of dag runs. Special handling is done
        to account for different task instance states that could be present when running
        them in a backfill process.
        :param ti_status: the internal status of the job
        :type ti_status: BackfillJob._DagRunTaskStatus
        :param executor: the executor to run the task instances
        :type executor: BaseExecutor
        :param pickle_id: the pickle_id if dag is pickled, None otherwise
        :type pickle_id: int
        :param start_date: the start date of the backfill job
        :type start_date: datetime.datetime
        :param session: the current session object
        :type session: sqlalchemy.orm.session.Session
        :return: the list of execution_dates for the finished dag runs
        :rtype: list
        """
        executed_run_dates = []