

**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
"""
        Override this method to cleanup subprocesses when a task instance
        gets killed. Any use of the threading, subprocess or multiprocessing
        module within an operator needs to be cleaned up or it will leave
        ghost processes behind.
        """
    def __deepcopy__(self, memo):
        """
        Hack sorting double chained task lists by task_id to avoid hitting
        max_depth on deepcopy operations.
        """
        sys.setrecursionlimit(5000)  
        cls = self.__class__
        result = cls.__new__(cls)
        memo[id(self)] = result
        shallow_copy = (
            cls.shallow_copy_attrs + cls._base_operator_shallow_copy_attrs
        )  
        for k, v in self.__dict__.items():
            if k not in shallow_copy:
                setattr(result, k, copy.deepcopy(v, memo))  
            else:
                setattr(result, k, copy.copy(v))
        return result
    def __getstate__(self):
        state = dict(self.__dict__)
        del state['_log']
        return state
    def __setstate__(self, state):