## 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
action = _create_action(name="$pageview", team=self.team)
        self._create_active_users_events()
        data = {
            "date_from": "2020-01-08",
            "date_to": "2020-01-19",
            "actions": [{"id": action.id, "type": "actions", "order": 0, "math": "weekly_active"}],
        }
        filter = Filter(data=data)
        result = Trends().run(filter, self.team)
        self.assertEqual(
            result[0]["days"],
            [
                "2020-01-08",
                "2020-01-09",
                "2020-01-10",
                "2020-01-11",
                "2020-01-12",
                "2020-01-13",
                "2020-01-14",
                "2020-01-15",
                "2020-01-16",
                "2020-01-17",
                "2020-01-18",
                "2020-01-19",
            ],
        )
        # 
        self.assertEqual(result[0]["data"], [1.0, 3.0, 2.0, 2.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 1.0, 0.0])
    @snapshot_clickhouse_queries
    def test_weekly_active_users_weekly(self):