**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
"""Executes Task (optionally with a Timeout) and pushes Xcom results"""
        
        
        if task_copy.execution_timeout:
            try:
                with timeout(task_copy.execution_timeout.total_seconds()):
                    result = task_copy.execute(context=context)
            except AirflowTaskTimeout:
                task_copy.on_kill()
                raise
        else:
            result = task_copy.execute(context=context)
        
        if task_copy.do_xcom_push and result is not None:
            self.xcom_push(key=XCOM_RETURN_KEY, value=result)
        return result
    def _run_execute_callback(self, context: Context, task):
        """Functions that need to be run before a Task is executed"""
        try:
            if task.on_execute_callback:
                task.on_execute_callback(context)
        except Exception:  
            self.log.exception("Failed when executing execute callback")
    def _run_finished_callback(self, error: Optional[Union[str, Exception]] = None) -> None: