## 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
person1, person2, person3, person4 = self._create_multiple_people()
        cohort = _create_cohort(
            name="cohort1",
            team=self.team,
            groups=[{"properties": [{"key": "name", "value": "person1", "type": "person"}]}],
        )
        cohort2 = _create_cohort(
            name="cohort2",
            team=self.team,
            groups=[{"properties": [{"key": "name", "value": "person2", "type": "person"}]}],
        )
        cohort3 = _create_cohort(
            name="cohort3",
            team=self.team,
            groups=[
                {"properties": [{"key": "name", "value": "person1", "type": "person"}]},
                {"properties": [{"key": "name", "value": "person2", "type": "person"}]},
            ],
        )
        action = _create_action(name="watched movie", team=self.team)
        with freeze_time("2020-01-04T13:01:01Z"):
            action_response = Trends().run(
                Filter(
                    data={
                        "date_from": "-14d",
                        "breakdown": json.dumps([cohort.pk, cohort2.pk, cohort3.pk, "all"]),
                        "breakdown_type": "cohort",
                        "actions": [{"id": action.pk, "type": "actions", "order": 0}],
                    }