## 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/utils.py
try:
        return datetime.datetime.strptime(input, "%Y-%m-%d").replace(tzinfo=pytz.UTC)
    except ValueError:
        pass
    
    
    try:
        return parser.isoparse(input).replace(tzinfo=pytz.UTC)
    except ValueError:
        pass
    regex = r"\-?(?P<number>[0-9]+)?(?P<type>[a-z])(?P<position>Start|End)?"
    match = re.search(regex, input)
    date = timezone.now()
    if not match:
        return date
    if match.group("type") == "h":
        date = date - relativedelta(hours=int(match.group("number")))
        return date.replace(minute=0, second=0, microsecond=0)
    elif match.group("type") == "d":
        if match.group("number"):
            date = date - relativedelta(days=int(match.group("number")))
    elif match.group("type") == "m":
        if match.group("number"):
            date = date - relativedelta(months=int(match.group("number")))
        if match.group("position") == "Start":