**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
self, dag: DAG, most_recent_dag_run: Optional[pendulum.DateTime], active_runs_of_dag: int
    ) -> None:
        """
        Calculate ``next_dagrun`` and `next_dagrun_create_after``
        :param dag: The DAG object
        :param most_recent_dag_run: DateTime of most recent run of this dag, or none if not yet scheduled.
        :param active_runs_of_dag: Number of currently active runs of this dag
        """
        self.next_dagrun, self.next_dagrun_create_after = dag.next_dagrun_info(most_recent_dag_run)
        if dag.max_active_runs and active_runs_of_dag >= dag.max_active_runs:
            
            log.debug(
                "DAG %s is at (or above) max_active_runs (%d of %d), not creating any more runs",
                dag.dag_id,
                active_runs_of_dag,
                dag.max_active_runs,
            )
            self.next_dagrun_create_after = None
        log.info("Setting next_dagrun for %s to %s", dag.dag_id, self.next_dagrun)
def dag(*dag_args, **dag_kwargs):
    """
    Python dag decorator. Wraps a function into an Airflow DAG.
    Accepts kwargs for operator kwarg. Can be used to parametrize DAGs.
    :param dag_args: Arguments for DAG object
    :type dag_args: Any
    :param dag_kwargs: Kwargs for DAG object.
    :type dag_kwargs: Any
    """
    def wrapper(f: Callable):