## 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
"name": "event_name",
                            "math": None,
                            "math_property": None,
                            "properties": [],
                        },
                        "label": "event_name",
                        "count": 4.0,
                        "data": [1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0],
                        "labels": [
                            "Sun. 1 November",
                            "Mon. 2 November",
                            "Tue. 3 November",
                            "Wed. 4 November",
                            "Thu. 5 November",
                            "Fri. 6 November",
                            "Sat. 7 November",
                        ],
                        "days": [
                            "2020-11-01",
                            "2020-11-02",
                            "2020-11-03",
                            "2020-11-04",
                            "2020-11-05",
                            "2020-11-06",
                            "2020-11-07",
                        ],
                    }
                ],
            )
        def test_week_interval(self):