**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
"""
    Sets the current execution context to the provided context object.
    This method should be called once per Task execution, before calling operator.execute.
    """
    _CURRENT_CONTEXT.append(context)
    try:
        yield context
    finally:
        expected_state = _CURRENT_CONTEXT.pop()
        if expected_state != context:
            log.warning(
                "Current context is not equal to the state at context stack. Expected=%s, got=%s",
                context,
                expected_state,
            )
def load_error_file(fd: IO[bytes]) -> Optional[Union[str, Exception]]:
    """Load and return error from error file"""
    fd.seek(0, os.SEEK_SET)
    data = fd.read()
    if not data:
        return None
    try:
        return pickle.loads(data)
    except Exception:  
        return "Failed to load task run error"
def set_error_file(error_file: str, error: Union[str, Exception]) -> None: