**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
"""
        Get the Default DAG View, returns the default config value if DagModel does not
        have a value
        """
        
        return self.default_view or conf.get('webserver', 'dag_default_view').lower()
    @property
    def safe_dag_id(self):
        return self.dag_id.replace('.', '__dot__')
    @provide_session
    def set_is_paused(self, is_paused: bool, including_subdags: bool = True, session=None) -> None:
        """
        Pause/Un-pause a DAG.
        :param is_paused: Is the DAG paused
        :param including_subdags: whether to include the DAG's subdags
        :param session: session
        """
        filter_query = [
            DagModel.dag_id == self.dag_id,
        ]
        if including_subdags:
            filter_query.append(DagModel.root_dag_id == self.dag_id)
        session.query(DagModel).filter(or_(*filter_query)).update(
            {DagModel.is_paused: is_paused}, synchronize_session='fetch'
        )
        session.commit()
    @classmethod
    @provide_session
    def deactivate_deleted_dags(cls, alive_dag_filelocs: List[str], session=None):