## 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
p1 = person_factory(team_id=self.team.pk, distinct_ids=["p1"], properties={"name": "p1"})
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-11T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-12T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-13T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-15T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-17T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p1", timestamp="2020-01-19T12:00:00Z",
            )
            p2 = person_factory(team_id=self.team.pk, distinct_ids=["p2"], properties={"name": "p2"})
            event_factory(
                team=self.team, event="$pageview", distinct_id="p2", timestamp="2020-01-09T12:00:00Z",
            )
            event_factory(
                team=self.team, event="$pageview", distinct_id="p2", timestamp="2020-01-12T12:00:00Z",
            )
            p3 = person_factory(team_id=self.team.pk, distinct_ids=["p3"], properties={"name": "p3"})
            event_factory(