**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
return result.strftime(fmt)
        return ''
    @provide_session
    def get_template_context(self, session=None) -> Context:  
        """Return TI Context"""
        task = self.task
        from airflow import macros
        integrate_macros_plugins()
        params = {}  
        run_id = ''
        dag_run = None
        if hasattr(task, 'dag'):
            if task.dag.params:
                params.update(task.dag.params)
            from airflow.models.dagrun import DagRun  
            dag_run = (
                session.query(DagRun)
                .filter_by(dag_id=task.dag.dag_id, execution_date=self.execution_date)
                .first()
            )
            run_id = dag_run.run_id if dag_run else None
            session.expunge_all()
            session.commit()
        ds = self.execution_date.strftime('%Y-%m-%d')
        ts = self.execution_date.isoformat()
        yesterday_ds = (self.execution_date - timedelta(1)).strftime('%Y-%m-%d')
        tomorrow_ds = (self.execution_date + timedelta(1)).strftime('%Y-%m-%d')