**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/taskinstance.py
self.refresh_from_task(task, pool_override=pool)
        self.refresh_from_db(session=session)
        self.job_id = job_id
        self.hostname = get_hostname()
        self.pid = os.getpid()
        session.merge(self)
        session.commit()
        actual_start_date = timezone.utcnow()
        Stats.incr(f'ti.start.{task.dag_id}.{task.task_id}')
        try:
            if not mark_success:
                context = self.get_template_context()
                self._prepare_and_execute_task_with_callbacks(context, task)
            self.refresh_from_db(lock_for_update=True)
            self.state = State.SUCCESS
        except AirflowSmartSensorException as e:
            self.log.info(e)
            return
        except AirflowSkipException as e:
            
            
            if e.args:
                self.log.info(e)
            self.refresh_from_db(lock_for_update=True)
            self.state = State.SKIPPED
            self.log.info(
                'Marking task as SKIPPED. '
                'dag_id=%s, task_id=%s, execution_date=%s, start_date=%s, end_date=%s',
                self.dag_id,
                self.task_id,