## 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
"2019-12-23",  
                "2019-12-24",  
                "2019-12-25",  
                "2019-12-26",  
                "2019-12-27",  
                "2019-12-28",  
            ],
        )
        self.assertEqual(response[1]["label"], "sign up")
        self.assertEqual(response[1]["labels"][3], "day 3")
        self.assertEqual(response[1]["data"][3], 1.0)
        self.assertEqual(response[1]["labels"][4], "day 4")
        self.assertEqual(response[1]["data"][4], 0.0)
        with freeze_time("2020-01-04T13:00:01Z"):
            no_compare_response = Trends().run(
                Filter(data={"compare": "false", "events": [{"id": "sign up"}]}), self.team
            )
        self.assertEqual(no_compare_response[0]["label"], "sign up")
        self.assertEqual(no_compare_response[0]["labels"][4], "1-Jan-2020")
        self.assertEqual(no_compare_response[0]["data"][4], 3.0)
        self.assertEqual(no_compare_response[0]["labels"][5], "2-Jan-2020")
        self.assertEqual(no_compare_response[0]["data"][5], 1.0)
    def test_trends_compare_day_interval_fixed_range_single(self):
        self._create_events(use_time=True)
        with freeze_time("2020-01-02T20:17:00Z"):
            response = Trends().run(
                Filter(
                    data={
                        "compare": "true",