Avoid side-effects in conf_vars testing helper

[Taragolis]

In pytest 8.0.0 the order of tests cases from @pytest.mark.parametrize executed in reversed order. This would be fixed in 8.0.1 (or whatewer version would be next):

• 8.0.0 reverses order of parametrize when calling individual tests  pytest-dev/pytest#11937

This regression in pytest shows that we have some side effects in conf_vars helper,
e.g. if run tests/providers/amazon/aws/log/test_cloudwatch_task_handler.py::TestCloudwatchTaskHandler::test_write_json_logs in pytest 8.0.0
or run it individually it would fail

❯ pytest "tests/providers/amazon/aws/log/test_cloudwatch_task_handler.py::TestCloudwatchTaskHandler::test_write_json_logs[not-set]"


======================================================================================================== test session starts ========================================================================================================
platform darwin -- Python 3.9.10, pytest-8.0.0, pluggy-1.3.0 -- /Users/taragolis/.pyenv/versions/3.9.10/envs/airflow-dev-env-39/bin/python
cachedir: .pytest_cache
rootdir: /Users/taragolis/Projects/common/airflow
configfile: pyproject.toml
plugins: anyio-4.0.0, instafail-0.5.0, forked-1.4.0, httpx-0.21.3, rerunfailures-12.0, timeouts-1.2.1, time-machine-2.13.0, cov-4.1.0, asyncio-0.21.1, mock-3.12.0, aiohttp-1.0.5, requests-mock-1.11.0, xdist-3.3.1, capture-warnings-0.0.4, icdiff-0.8
asyncio: mode=strict
setup timeout: 0.0s, execution timeout: 0.0s, teardown timeout: 0.0s
collected 1 item                                                                                                                                                                                                                    

tests/providers/amazon/aws/log/test_cloudwatch_task_handler.py::TestCloudwatchTaskHandler::test_write_json_logs[not-set] FAILED                                                                                               [100%]

============================================================================================================= FAILURES ==============================================================================================================
______________________________________________________________________________________ TestCloudwatchTaskHandler.test_write_json_logs[not-set] ______________________________________________________________________________________

self = <tests.providers.amazon.aws.log.test_cloudwatch_task_handler.TestCloudwatchTaskHandler object at 0x116b632e0>, mock_get_log_events = <MagicMock name='get_log_events' id='4843681872'>, conf_json_serialize = None
expected_serialized_output = '{"datetime": "2023-01-01T00:00:00+00:00", "customObject": null}'

    @pytest.mark.parametrize(
        "conf_json_serialize, expected_serialized_output",
        [
            pytest.param(
                "airflow.providers.amazon.aws.log.cloudwatch_task_handler.json_serialize_legacy",
                '{"datetime": "2023-01-01T00:00:00+00:00", "customObject": null}',
                id="json-serialize-legacy",
            ),
            pytest.param(
                "airflow.providers.amazon.aws.log.cloudwatch_task_handler.json_serialize",
                '{"datetime": "2023-01-01T00:00:00+00:00", "customObject": "SomeCustomSerialization(...)"}',
                id="json-serialize",
            ),
            pytest.param(
                None, '{"datetime": "2023-01-01T00:00:00+00:00", "customObject": null}', id="not-set"
            ),
        ],
    )
    @mock.patch.object(AwsLogsHook, "get_log_events")
    def test_write_json_logs(self, mock_get_log_events, conf_json_serialize, expected_serialized_output):
        class ToSerialize:
            def __init__(self):
                pass
    
            def __repr__(self):
                return "SomeCustomSerialization(...)"
    
        with conf_vars({("aws", "cloudwatch_task_handler_json_serializer"): conf_json_serialize}):
            handler = self.cloudwatch_task_handler
            handler.set_context(self.ti)
            message = logging.LogRecord(
                name="test_log_record",
                level=logging.DEBUG,
                pathname="fake.path",
                lineno=42,
                args=None,
                exc_info=None,
                msg={
                    "datetime": datetime(2023, 1, 1),
                    "customObject": ToSerialize(),
                },
            )
            with mock.patch("watchtower.threading.Thread"), mock.patch("watchtower.queue.Queue") as mq:
                mock_queue = Mock()
                mq.return_value = mock_queue
                handler.handle(message)
>               mock_queue.put.assert_called_once_with(
                    {"message": expected_serialized_output, "timestamp": ANY}
                )

tests/providers/amazon/aws/log/test_cloudwatch_task_handler.py:220: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../../../.pyenv/versions/3.9.10/lib/python3.9/contextlib.py:126: in __exit__
    next(self.gen)
tests/test_utils/config.py:52: in conf_vars
    conf.set(section, key, value)
airflow/configuration.py:1304: in set
    super().set(section, option, value)
../../../.pyenv/versions/3.9.10/lib/python3.9/configparser.py:1204: in set
    super().set(section, option, value)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <airflow.configuration.AirflowConfigParser object at 0x110067f10>, section = 'aws', option = 'cloudwatch_task_handler_json_serializer'
value = 'airflow.providers.amazon.aws.log.cloudwatch_task_handler.json_serialize_legacy'

    def set(self, section, option, value=None):
        """Set an option."""
        if value:
            value = self._interpolation.before_set(self, section, option,
                                                   value)
        if not section or section == self.default_section:
            sectdict = self._defaults
        else:
            try:
                sectdict = self._sections[section]
            except KeyError:
>               raise NoSectionError(section) from None
E               configparser.NoSectionError: No section: 'aws'

It might not reproduced in CI, because some other tests adds some side effects ¯\_(ツ)_/¯ as result this and maybe others tests completed succesefully

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