

**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
"""
        Set a task or a task list to be directly downstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=False)
    def set_upstream(self, task_or_task_list: Union[TaskMixin, Sequence[TaskMixin]]) -> None:
        """
        Set a task or a task list to be directly upstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=True)
    @property
    def output(self):