## 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()
        # 
        with freeze_time("2020-01-04T13:01:01Z"):
            response = Trends().run(
                Filter(
                    data={
                        "date_from": "-7d",
                        "breakdown": "$some_property",
                        "events": [{"id": "sign up", "name": "sign up", "type": "events", "order": 0}],
                        "display": TRENDS_BAR_VALUE,
                    }
                ),
                self.team,
            )
        self.assertEqual(response[0]["aggregated_value"], 2)  # 
        self.assertEqual(response[1]["aggregated_value"], 1)
        self.assertEqual(response[2]["aggregated_value"], 1)
        self.assertEqual(
            response[0]["days"],
            [
                "2019-12-28",
                "2019-12-29",
                "2019-12-30",
                "2019-12-31",
                "2020-01-01",
                "2020-01-02",