## 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
cohort1 = _create_cohort(
            team=self.team,
            name="cohort_1",
            groups=[{"properties": [{"key": "key", "value": "value", "type": "person"}]}],
        )
        cohort2 = _create_cohort(
            team=self.team,
            name="cohort_2",
            groups=[{"properties": [{"key": "key_2", "value": "value_2", "type": "person"}]}],
        )
        cohort1.calculate_people_ch(pending_version=0)
        cohort2.calculate_people_ch(pending_version=0)
        with self.settings(USE_PRECALCULATED_CH_COHORT_PEOPLE=True):  # 
            with freeze_time("2020-01-04T13:01:01Z"):
                res = Trends().run(
                    Filter(
                        data={
                            "date_from": "-7d",
                            "events": [{"id": "$pageview"}],
                            "properties": [],
                            "breakdown": [cohort1.pk, cohort2.pk],
                            "breakdown_type": "cohort",
                        }
                    ),
                    self.team,
                )
        self.assertEqual(res[0]["count"], 2)
        self.assertEqual(res[1]["count"], 1)
    @test_with_materialized_columns(person_properties=["key", "key_2"], verify_no_jsonextract=False)
    def test_breakdown_single_cohort(self):