## 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
"7-Nov-2020",
                        "8-Nov-2020",
                        "9-Nov-2020",
                        "10-Nov-2020",
                        "11-Nov-2020",
                        "12-Nov-2020",
                        "13-Nov-2020",
                        "14-Nov-2020",
                    ],
                    "days": [
                        "2020-10-31",
                        "2020-11-01",
                        "2020-11-02",
                        "2020-11-03",
                        "2020-11-04",
                        "2020-11-05",
                        "2020-11-06",
                        "2020-11-07",
                        "2020-11-08",
                        "2020-11-09",
                        "2020-11-10",
                        "2020-11-11",
                        "2020-11-12",
                        "2020-11-13",
                        "2020-11-14",
                    ],
                }
            ],
        )
    def test_last30days_timerange(self):