

**Description**

We are using a 3rd party executor which has the ability to use multiple queues, however the `default_queue` is defined under the `celery` heading and is used regardless of the executor that you are using.

See: https://github.com/apache/airflow/blob/2.0.1/airflow/models/baseoperator.py#L366

It would be nice to decouple the default_queue configuration argument away from the celery section to allow other executors to utilise this functionality with less confusion.

**Are you willing to submit a PR?**

Yep! Will open a pull request shortly


**Related Issues**

Not that I'm aware of.

airflow/models/baseoperator.py
self,
        upstream: bool = False,
        found_descendants: Optional[Set[str]] = None,
    ) -> Set[str]:
        """Get a flat set of relatives' ids, either upstream or downstream."""
        if not self._dag:
            return set()
        if not found_descendants:
            found_descendants = set()
        relative_ids = self.get_direct_relative_ids(upstream)
        for relative_id in relative_ids:
            if relative_id not in found_descendants:
                found_descendants.add(relative_id)
                relative_task = self._dag.task_dict[relative_id]
                relative_task.get_flat_relative_ids(upstream, found_descendants)
        return found_descendants
    def get_flat_relatives(self, upstream: bool = False):
        """Get a flat list of relatives, either upstream or downstream."""
        if not self._dag:
            return set()
        from airflow.models.dag import DAG
        dag: DAG = self._dag
        return list(map(lambda task_id: dag.task_dict[task_id], self.get_flat_relative_ids(upstream)))
    def run(