## 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
)
        _create_event(
            team=self.team,
            event="sign up",
            distinct_id="blabla",
            properties={"$session_id": 4},
            timestamp="2020-01-02 00:06:45",
        )
        
        with freeze_time("2020-01-04T13:00:01Z"):
            response = Trends().run(
                Filter(
                    data={
                        "display": "ActionsLineGraph",
                        "interval": "day",
                        "events": [{"id": "sign up", "math": "unique_session"}],
                        "breakdown": "$session_duration",
                        "breakdown_type": "session",
                        "insight": "TRENDS",
                        "breakdown_histogram_bin_count": 3,
                        "properties": [{"key": "$some_prop", "value": "some_val", "type": "person"}],
                        "date_from": "-3d",
                    }
                ),
                self.team,
            )
            self.assertEqual(
                [(item["breakdown_value"], item["count"], item["data"]) for item in response],
                [
                    ("[0.0,4.95]", 1.0, [1.0, 0.0, 0.0, 0.0]),