## 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
team = kwargs.pop("team")
    name = kwargs.pop("name")
    properties = kwargs.pop("properties", {})
    action = Action.objects.create(team=team, name=name)
    ActionStep.objects.create(action=action, event=name, properties=properties)
    return action
def _create_cohort(**kwargs):
    team = kwargs.pop("team")
    name = kwargs.pop("name")
    groups = kwargs.pop("groups")
    cohort = Cohort.objects.create(team=team, name=name, groups=groups, last_calculation=timezone.now())
    return cohort
class TestTrends(ClickhouseTestMixin, APIBaseTest):
    maxDiff = None
    def _get_trend_people(self, filter: Filter, entity: Entity):
        data = filter.to_dict()
        
        if data.get("events", None):
            data["events"] = json.dumps(data["events"])
        if data.get("properties", None):
            data["properties"] = json.dumps(data["properties"])
        with self.settings(DEBUG=True):
            response = self.client.get(
                f"/api/projects/{self.team.id}/persons/trends/",
                data={**data, ENTITY_TYPE: entity.type, ENTITY_ID: entity.id},
                content_type="application/json",
            ).json()
        return response["results"][0]["people"]
    def _create_events(self, use_time=False) -> Tuple[Action, Person]: