## 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._test_events_with_dates(
                dates=["2020-06-01", "2020-07-10", "2020-07-30", "2020-10-18"],
                interval="month",
                date_from="2020-6-01",
                date_to="2020-11-24",
                result=[
                    {
                        "action": {
                            "id": "event_name",
                            "type": "events",
                            "order": None,
                            "name": "event_name",
                            "math": None,
                            "math_property": None,
                            "properties": [],
                        },
                        "label": "event_name",
                        "count": 4.0,
                        "data": [1.0, 2.0, 0.0, 0.0, 1.0, 0.0],
                        "labels": [
                            "Mon. 1 June",
                            "Wed. 1 July",
                            "Sat. 1 August",
                            "Tue. 1 September",
                            "Thu. 1 October",
                            "Sun. 1 November",
                        ],