**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
"""Returns a boolean indicating whether this DAG is paused"""
        qry = session.query(DagModel).filter(DagModel.dag_id == self.dag_id)
        return qry.value(DagModel.is_paused)
    @property
    def is_paused(self):
        """This attribute is deprecated. Please use `airflow.models.DAG.get_is_paused` method."""
        warnings.warn(
            "This attribute is deprecated. Please use `airflow.models.DAG.get_is_paused` method.",
            DeprecationWarning,
            stacklevel=2,
        )
        return self.get_is_paused()
    @property
    def normalized_schedule_interval(self) -> Optional[ScheduleInterval]:
        """
        Returns Normalized Schedule Interval. This is used internally by the Scheduler to
        schedule DAGs.
        1. Converts Cron Preset to a Cron Expression (e.g ``@monthly`` to ``0 0 1 * *``)
        2. If Schedule Interval is "@once" return "None"
        3. If not (1) or (2) returns schedule_interval
        """
        if isinstance(self.schedule_interval, str) and self.schedule_interval in cron_presets:
            _schedule_interval = cron_presets.get(self.schedule_interval)  
        elif self.schedule_interval == '@once':
            _schedule_interval = None
        else:
            _schedule_interval = self.schedule_interval
        return _schedule_interval
    @provide_session
    def handle_callback(self, dagrun, success=True, reason=None, session=None):