**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/api_connexion/endpoints/task_instance_endpoint.py
limit: int,
    dag_id: Optional[str] = None,
    dag_run_id: Optional[str] = None,
    execution_date_gte: Optional[str] = None,
    execution_date_lte: Optional[str] = None,
    start_date_gte: Optional[str] = None,
    start_date_lte: Optional[str] = None,
    end_date_gte: Optional[str] = None,
    end_date_lte: Optional[str] = None,
    duration_gte: Optional[float] = None,
    duration_lte: Optional[float] = None,
    state: Optional[str] = None,
    pool: Optional[List[str]] = None,
    queue: Optional[List[str]] = None,
    offset: Optional[int] = None,
    session=None,
):  
    """Get list of task instances."""
    base_query = session.query(TI)
    if dag_id != "~":
        base_query = base_query.filter(TI.dag_id == dag_id)
    if dag_run_id != "~":
        base_query = base_query.join(DR, and_(TI.dag_id == DR.dag_id, TI.execution_date == DR.execution_date))
        base_query = base_query.filter(DR.run_id == dag_run_id)
    base_query = _apply_range_filter(
        base_query,