

**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/configuration.py
return old.search(current_value) is not None
    def _update_env_var(self, section, name, new_value):
        
        
        env_var = self._env_var_name(section, name)
        os.environ.pop(env_var, None)
        self.set(section, name, new_value)
    @staticmethod
    def _create_future_warning(name, section, current_value, new_value, version):
        warnings.warn(
            'The {name} setting in [{section}] has the old default value '
            'of {current_value!r}. This value has been changed to {new_value!r} in the '
            'running config, but please update your config before Apache '
            'Airflow {version}.'.format(
                name=name, section=section, current_value=current_value, new_value=new_value, version=version
            ),
            FutureWarning,
        )
    ENV_VAR_PREFIX = 'AIRFLOW__'
    def _env_var_name(self, section: str, key: str) -> str: