

**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
"""Getting the content of files for template_field / template_ext"""
        if self.template_ext:  
            for field in self.template_fields:
                content = getattr(self, field, None)
                if content is None:  
                    continue
                elif isinstance(content, str) and any(content.endswith(ext) for ext in self.template_ext):
                    env = self.get_template_env()
                    try:
                        setattr(self, field, env.loader.get_source(env, content)[0])
                    except Exception as e:  
                        self.log.exception(e)
                elif isinstance(content, list):
                    env = self.dag.get_template_env()
                    for i in range(len(content)):  
                        if isinstance(content[i], str) and any(
                            content[i].endswith(ext) for ext in self.template_ext
                        ):
                            try:
                                content[i] = env.loader.get_source(env, content[i])[0]
                            except Exception as e:  
                                self.log.exception(e)
        self.prepare_template()
    @property
    def upstream_list(self) -> List["BaseOperator"]: