**Apache Airflow version**:

2.0.1

**What happened**:

When clearing task across dags using `ExternalTaskMarker` the dag state of the external `DagRun` is not set to active. So cleared tasks in the external dag will not automatically start if the `DagRun` is a Failed or Succeeded state.

**What you expected to happen**:

The external `DagRun` run should also be set to Running state.

**How to reproduce it**:

Clear tasks in an external dag using an ExternalTaskMarker.


**Anything else we need to know**:

Looking at the code is has:

https://github.com/apache/airflow/blob/b23fc137812f5eabf7834e07e032915e2a504c17/airflow/models/dag.py#L1323-L1335

It seems like it intentionally calls the dag member method `set_dag_run_state` instead of letting the helper function `clear_task_insntances` set the `DagRun` state. But the member method will only change the state of `DagRun`s of dag where the original task is, while I believe `clear_task_instances` would correctly change the state of all involved `DagRun`s.

airflow/models/dag.py
return session.query(DagModel).filter(DagModel.dag_id == dag_id).first()
    @classmethod
    @provide_session
    def get_current(cls, dag_id, session=None):
        return session.query(cls).filter(cls.dag_id == dag_id).first()
    @provide_session
    def get_last_dagrun(self, session=None, include_externally_triggered=False):
        return get_last_dagrun(
            self.dag_id, session=session, include_externally_triggered=include_externally_triggered
        )
    @staticmethod
    @provide_session
    def get_paused_dag_ids(dag_ids: List[str], session: Session = None) -> Set[str]:
        """
        Given a list of dag_ids, get a set of Paused Dag Ids
        :param dag_ids: List of Dag ids
        :param session: ORM Session
        :return: Paused Dag_ids
        """
        paused_dag_ids = (
            session.query(DagModel.dag_id)
            .filter(DagModel.is_paused == expression.true())
            .filter(DagModel.dag_id.in_(dag_ids))
            .all()
        )
        paused_dag_ids = {paused_dag_id for paused_dag_id, in paused_dag_ids}
        return paused_dag_ids
    def get_default_view(self) -> str: