

**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 f'{self.ENV_VAR_PREFIX}{section.upper()}__{key.upper()}'
    def _get_env_var_option(self, section, key):
        
        env_var = self._env_var_name(section, key)
        if env_var in os.environ:
            return expand_env_var(os.environ[env_var])
        
        env_var_cmd = env_var + '_CMD'
        if env_var_cmd in os.environ:
            
            if (section, key) in self.sensitive_config_values:
                return run_command(os.environ[env_var_cmd])
        
        env_var_secret_path = env_var + '_SECRET'
        if env_var_secret_path in os.environ:
            
            if (section, key) in self.sensitive_config_values:
                return _get_config_value_from_secret_backend(os.environ[env_var_secret_path])
        return None
    def _get_cmd_option(self, section, key):
        fallback_key = key + '_cmd'
        
        if (section, key) in self.sensitive_config_values:
            if super().has_option(section, fallback_key):
                command = super().get(section, fallback_key)
                return run_command(command)
        return None
    def _get_secret_option(self, section, key):