## 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
weekly_response[0]["labels"],
            [
                "30-Dec-2019",
                "31-Dec-2019",
                "1-Jan-2020",
                "2-Jan-2020",
                "3-Jan-2020",
                "4-Jan-2020",
                "5-Jan-2020",
                "6-Jan-2020",
            ],
        )
        ONE_DAY_IN_SECONDS = 24 * 60 * 60
        
        
        self.assertCountEqual(
            weekly_response[0]["data"],
            [
                0,
                0,
                3 * ONE_DAY_IN_SECONDS,
                2 * ONE_DAY_IN_SECONDS,
                2 * ONE_DAY_IN_SECONDS,
                0,
                4 * ONE_DAY_IN_SECONDS,
                0,
            ],
        )
    @test_with_materialized_columns(person_properties=["name"])
    def test_filter_events_by_cohort(self):