**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
self,
        state: str = State.RUNNING,
        session: Session = None,
        start_date: Optional[datetime] = None,
        end_date: Optional[datetime] = None,
        dag_ids: List[str] = None,
    ) -> None:
        dag_ids = dag_ids or [self.dag_id]
        query = session.query(DagRun).filter(DagRun.dag_id.in_(dag_ids))
        if start_date:
            query = query.filter(DagRun.execution_date >= start_date)
        if end_date:
            query = query.filter(DagRun.execution_date <= end_date)
        query.update({DagRun.state: state}, synchronize_session='fetch')
    @provide_session
    def clear(