## 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)`.

#### *Thank you* for your bug report – we love squashing them!

posthog/queries/test/test_trends.py
self._test_events_with_dates(
            dates=["2020-11-01 05:20:00", "2020-11-01 10:22:00", "2020-11-01 10:25:00", "2020-11-02 08:25:00"],
            date_from="-48h",
            query_time="2020-11-02 10:20:00",
            result=[
                {
                    "action": {
                        "id": "event_name",
                        "type": "events",
                        "order": None,
                        "name": "event_name",
                        "custom_name": None,
                        "math": None,
                        "math_property": None,
                        "math_group_type_index": None,
                        "properties": [],
                    },
                    "label": "event_name",
                    "count": 4.0,
                    "data": [0.0, 3.0, 1.0],
                    "labels": ["31-Oct-2020", "1-Nov-2020", "2-Nov-2020"],
                    "days": ["2020-10-31", "2020-11-01", "2020-11-02"],
                }
            ],
        )
    def test_last7days_timerange(self):