## 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.team.timezone = "US/Pacific"
        self.team.save()
        self._create_event_count_per_user_events()
        with freeze_time("2020-01-03 19:06:34"):
            _create_person(team_id=self.team.pk, distinct_ids=["another_user"])
            _create_event(
                team=self.team, event="viewed video", distinct_id="another_user", properties={"color": "orange"}
            )
        daily_response = Trends().run(
            Filter(
                data={
                    "display": TRENDS_LINEAR,
                    "events": [{"id": "viewed video", "math": "dau"}],
                    "breakdown": "color",
                    "date_from": "2020-01-01",
                    "date_to": "2020-03-07",
                    "interval": "month",
                }
            ),
            self.team,
        )
        # as
        assert daily_response[0]["days"] == ["2020-01-01", "2020-02-01", "2020-03-01"]
        assert daily_response[1]["days"] == ["2020-01-01", "2020-02-01", "2020-03-01"]
        assert daily_response[2]["days"] == ["2020-01-01", "2020-02-01", "2020-03-01"]
    def test_trends__per_user_average_with_event_property_breakdown(self):
        self._create_event_count_per_user_events()
        daily_response = Trends().run(