## 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
# 
        sign_up_action, _ = self._create_events()
        flush_persons_and_events()
        cohort = Cohort.objects.create(
            team=self.team,
            name="a",
            groups=[{"properties": [{"key": "$some_prop", "value": "some_val", "type": "person"}]}],
        )
        step = sign_up_action.steps.first()
        if step:
            step.properties = [{"key": "id", "value": cohort.pk, "type": "cohort"}]
            step.save()
        with freeze_time("2020-01-04T13:01:01Z"):
            action_response = Trends().run(
                Filter(data={"actions": [{"id": sign_up_action.id}], "breakdown": "$some_property"}), self.team
            )
        self.assertEqual(action_response[0]["count"], 2)
    @test_with_materialized_columns(event_properties=["key"], person_properties=["email"])
    def test_breakdown_user_props_with_filter(self):