## 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
team=self.team, event="$pageview", distinct_id="p3", timestamp="2020-01-12T12:00:00Z",
            )
            p4 = person_factory(team_id=self.team.pk, distinct_ids=["p4"], properties={"name": "p4"})
            event_factory(
                team=self.team, event="$pageview", distinct_id="p4", timestamp="2020-01-15T12:00:00Z",
            )
            with freeze_time("2020-01-17T13:01:01Z"):
                result = trends().run(
                    Filter(
                        data={
                            "date_from": "all",
                            "events": [{"id": "$pageview", "type": "events", "order": 0}],
                            "shown_as": TRENDS_LIFECYCLE,
                        }
                    ),
                    self.team,
                )
            for res in result:
                if res["status"] == "dormant":
                    self.assertEqual(res["data"], [0, -1, 0, 0, -2, -1, 0, -2, 0])
                elif res["status"] == "returning":
                    self.assertEqual(res["data"], [0, 0, 0, 1, 1, 0, 0, 0, 0])
                elif res["status"] == "resurrecting":
                    self.assertEqual(res["data"], [0, 0, 0, 1, 0, 0, 1, 0, 1])
                elif res["status"] == "new":
                    self.assertEqual(res["data"], [1, 0, 1, 1, 0, 0, 1, 0, 0])
        def test_lifecycle_trend_weeks(self):
            
            p1 = person_factory(team_id=self.team.pk, distinct_ids=["p1"], properties={"name": "p1"})
            event_factory(