**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 self._executor_config
    @provide_session
    def construct_task_instance(self, session=None, lock_for_update=False) -> TaskInstance:
        """
        Construct a TaskInstance from the database based on the primary key
        :param session: DB session.
        :param lock_for_update: if True, indicates that the database should
            lock the TaskInstance (issuing a FOR UPDATE clause) until the
            session is committed.
        :return: the task instance constructed
        """
        qry = session.query(TaskInstance).filter(
            TaskInstance.dag_id == self._dag_id,
            TaskInstance.task_id == self._task_id,
            TaskInstance.execution_date == self._execution_date,
        )
        if lock_for_update:
            ti = qry.with_for_update().first()
        else:
            ti = qry.first()
        return ti
STATICA_HACK = True
globals()['kcah_acitats'[::-1].upper()] = False
if STATICA_HACK:  
    from airflow.job.base_job import BaseJob
    from airflow.models.dagrun import DagRun
    TaskInstance.dag_run = relationship(DagRun)
    TaskInstance.queued_by_job = relationship(BaseJob)