## Bug description

When calculating Trends results with an aggregated (e.g. single output, like big number) display type, WAU/MAU don't work. This is because we have an `ACTIVE_USERS_SQL` query for time series display types, but we don't have a version of this for aggregated display types. (See ZEN-1043.)

## How to reproduce

1. Create an insight with a single WAU or MAU series.
2. Switch display type to "Number".
3. Open the "Debug ClickHouse queries" modal from the command palette.
4. See `COUNT(*)` instead of `COUNT(DISTINCT person_id)`.

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posthog/queries/test/test_trends.py
self._create_events()
        flush_persons_and_events()
        response = Trends().run(Filter(data={"date_from": "2012-12-12"}), self.team)
        self.assertEqual(response, [])
    def test_interval_filtering(self):
        self._create_events(use_time=True)
        
        with freeze_time("2020-01-02"):
            response = Trends().run(
                Filter(data={"date_from": "2019-12-24", "interval": "hour", "events": [{"id": "sign up"}]}),
                self.team,
            )
        self.assertEqual(response[0]["labels"][3], "24-Dec-2019 03:00")
        self.assertEqual(response[0]["data"][3], 1.0)
        
        self.assertEqual(response[0]["data"][192], 3.0)
        
        with freeze_time("2020-01-02"):
            response = Trends().run(
                Filter(
                    data={
                        
                        "date_from": "2019-11-24",
                        "interval": "week",
                        "events": [{"id": "sign up"}],