## 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
sign_up_action, _ = self._create_events()
            with freeze_time("2020-01-02"):
                event_factory(
                    team=self.team, event="sign up", distinct_id="blabla", properties={"$some_property": "other_value"},
                )
            with freeze_time("2020-01-04"):
                action_response = trends().run(
                    Filter(data={"breakdown": "$some_property", "actions": [{"id": sign_up_action.id, "math": "dau"}]}),
                    self.team,
                )
                event_response = trends().run(
                    Filter(data={"breakdown": "$some_property", "events": [{"id": "sign up", "math": "dau"}]}),
                    self.team,
                )
            self.assertEqual(event_response[0]["label"], "sign up - other_value")
            self.assertEqual(event_response[1]["label"], "sign up - value")
            self.assertEqual(event_response[2]["label"], "sign up - Other")
            self.assertEqual(sum(event_response[0]["data"]), 1)
            self.assertEqual(event_response[0]["data"][5], 1)
            self.assertEqual(sum(event_response[2]["data"]), 1)
            self.assertEqual(event_response[2]["data"][4], 1)  
            self.assertTrue(self._compare_entity_response(action_response, event_response))
        def _create_maths_events(self, values):