**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
"""
        Call callback defined for finished state change.
        NOTE: Only invoke this function from caller of self._run_raw_task or
        self.run
        """
        if self.state == State.FAILED:
            task = self.task
            if task.on_failure_callback is not None:
                context = self.get_template_context()
                context["exception"] = error
                task.on_failure_callback(context)
        elif self.state == State.SUCCESS:
            task = self.task
            if task.on_success_callback is not None:
                context = self.get_template_context()
                task.on_success_callback(context)
        elif self.state == State.UP_FOR_RETRY:
            task = self.task
            if task.on_retry_callback is not None:
                context = self.get_template_context()
                context["exception"] = error
                task.on_retry_callback(context)
    @provide_session
    def run(