Fix DbApiHook.insert_rows when rows is a generator

[vincbeck]

#38715 introduced a bug when the parameter rows is a generator. In that case, the method raises this error:

ERROR [airflow.task] Task failed with exception
Traceback (most recent call last):
  File "/opt/airflow/airflow/models/taskinstance.py", line 478, in _execute_task
    result = _execute_callable(context=context, **execute_callable_kwargs)
  File "/opt/airflow/airflow/models/taskinstance.py", line 441, in _execute_callable
    return ExecutionCallableRunner(
  File "/opt/airflow/airflow/utils/operator_helpers.py", line 250, in run
    return self.func(*args, **kwargs)
  File "/opt/airflow/airflow/models/baseoperator.py", line 405, in wrapper
    return func(self, *args, **kwargs)
  File "/opt/airflow/airflow/providers/amazon/aws/transfers/s3_to_sql.py", line 115, in execute
    self.db_hook.insert_rows(
  File "/opt/airflow/airflow/providers/common/sql/hooks/sql.py", line 597, in insert_rows
    self.log.info("Done loading. Loaded a total of %s rows into %s", len(rows), table)
TypeError: object of type 'generator' has no len()

Our system test example_s3_to_sql is failing because of that.

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[o-nikolas]

Have you run the system test locally to ensure it passes with this new code change?

[vincbeck]

Have you run the system test locally to ensure it passes with this new code change?

Yes sir!

[dabla]

As promised I created a PR which also checks the insert_rows method when an iterator is passed as rows parameter.