## Is your feature request related to a problem?

There's only 2 files where we use pandas, but pandas is 49MB and numpy is another 86MB, slowing down builds massively.

## Describe the solution you'd like

Replace pandas with a pure SQL/Python solution in
- posthog/queries/trends.py
- posthog/queries/sessions.py

Both of those have equivalent examples in Clickhouse (ee/clickhouse) that don't use Pandas.

## Describe alternatives you've considered

Continue using Pandas and clogging builds

## Additional context



#### *Thank you* for your feature request – we love each and every one!

posthog/queries/test/test_trends.py
"Sun. 1 November, 14:00",
                            "Sun. 1 November, 15:00",
                            "Sun. 1 November, 16:00",
                            "Sun. 1 November, 17:00",
                            "Sun. 1 November, 18:00",
                        ],
                        "days": [
                            "2020-11-01 12:00:00",
                            "2020-11-01 13:00:00",
                            "2020-11-01 14:00:00",
                            "2020-11-01 15:00:00",
                            "2020-11-01 16:00:00",
                            "2020-11-01 17:00:00",
                            "2020-11-01 18:00:00",
                        ],
                    }
                ],
            )
        def test_day_interval(self):
            self._test_events_with_dates(
                dates=["2020-11-01", "2020-11-02", "2020-11-03", "2020-11-04"],
                interval="day",
                date_from="2020-11-01",
                date_to="2020-11-07",
                result=[
                    {
                        "action": {
                            "id": "event_name",
                            "type": "events",
                            "order": None,