## 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
_create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p1",
            timestamp="2020-01-10T12:00:00Z",
            properties={"key": "val"},
        )
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p1",
            timestamp="2020-01-11T12:00:00Z",
            properties={"key": "val"},
        )
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p2",
            timestamp="2020-01-11T12:00:00Z",
            properties={"key": "val"},
        )
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p0",
            timestamp="2020-01-12T12:00:00Z",
            properties={"key": "val"},
        )
    @snapshot_clickhouse_queries
    def test_weekly_active_users_monthly(self):