## 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
self._create_events()
            with freeze_time("2020-01-04T13:00:01Z"):
                response = trends().run(Filter(data={"compare": "true", "events": [{"id": "sign up"}]}), self.team)
            self.assertEqual(response[0]["label"], "sign up - current")
            self.assertEqual(response[0]["labels"][4], "day 4")
            self.assertEqual(response[0]["data"][4], 3.0)
            self.assertEqual(response[0]["labels"][5], "day 5")
            self.assertEqual(response[0]["data"][5], 1.0)
            self.assertEqual(response[1]["label"], "sign up - previous")
            self.assertEqual(response[1]["labels"][4], "day 4")
            self.assertEqual(response[1]["data"][4], 1.0)
            self.assertEqual(response[1]["labels"][5], "day 5")
            self.assertEqual(response[1]["data"][5], 0.0)
            with freeze_time("2020-01-04T13:00:01Z"):
                no_compare_response = trends().run(
                    Filter(data={"compare": "false", "events": [{"id": "sign up"}]}), self.team
                )
            self.assertEqual(no_compare_response[0]["label"], "sign up")
            self.assertEqual(no_compare_response[0]["labels"][4], "Wed. 1 January")
            self.assertEqual(no_compare_response[0]["data"][4], 3.0)
            self.assertEqual(no_compare_response[0]["labels"][5], "Thu. 2 January")
            self.assertEqual(no_compare_response[0]["data"][5], 1.0)
        def _test_events_with_dates(self, dates: List[str], result, query_time=None, **filter_params):