**Description**
The Airflow logs generated by the Livy operator currently only state the status of the submitted batch. To view the logs from the job itself, one must go separately to the session logs. I think that Airflow should have the option (possibly on by default) that retrieves the session logs after the batch reaches a terminal state if a `polling_interval` has been set.

**Use case / motivation**
When debugging a task submitted via Livy, the session logs are the first place to check. For most other tasks, including SparkSubmitOperator, viewing the first-check logs can be done in the Airflow UI, but for Livy you must go externally or write a separate task to retrieve them. 

**Are you willing to submit a PR?**

I don't yet have a good sense of how challenging this will be to set up and test. I can try but if anyone else wants to go for it, don't let my attempt stop you.

**Related Issues**

None I could find

airflow/providers/apache/livy/operators/livy.py
self._batch_id = self.get_hook().post_batch(**self.spark_params)
        if self._polling_interval > 0:
            self.poll_for_termination(self._batch_id)
        return self._batch_id
    def poll_for_termination(self, batch_id: Union[int, str]) -> None:
        """
        Pool Livy for batch termination.
        :param batch_id: id of the batch session to monitor.
        :type batch_id: int
        """
        hook = self.get_hook()
        state = hook.get_batch_state(batch_id)
        while state not in hook.TERMINAL_STATES:
            self.log.debug('Batch with id %s is in state: %s', batch_id, state.value)
            sleep(self._polling_interval)
            state = hook.get_batch_state(batch_id)
        self.log.info("Batch with id %s terminated with state: %s", batch_id, state.value)
        if state != BatchState.SUCCESS:
            raise AirflowException(f"Batch {batch_id} did not succeed")
    def on_kill(self) -> None:
        self.kill()
    def kill(self) -> None:
        """Delete the current batch session."""
        if self._batch_id is not None:
            self.get_hook().delete_batch(self._batch_id)