## 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
"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,  # 
            ],
        )
    def test_weekly_active_users_daily_based_on_action(self):