**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
self.state = state
        self.hostname = ''
        self.init_on_load()
        
        
        self.raw = False
        
        self.test_mode = False
    @reconstructor
    def init_on_load(self):
        """Initialize the attributes that aren't stored in the DB"""
        self.test_mode = False  
    @property
    def try_number(self):
        """
        Return the try number that this task number will be when it is actually
        run.
        If the TaskInstance is currently running, this will match the column in the
        database, in all other cases this will be incremented.
        """
        
        
        if self.state in State.running:
            return self._try_number
        return self._try_number + 1
    @try_number.setter
    def try_number(self, value):
        self._try_number = value
    @property
    def prev_attempted_tries(self):