## 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_person(
            team_id=self.team.pk, distinct_ids=["blabla", "anonymous_id"], properties={"$some_prop": "some_val"}
        )
        _create_person(team_id=self.team.pk, distinct_ids=["blabla2"], properties={"$some_prop": "some_val"})
        _create_event(
            team=self.team,
            event="sign up before",
            distinct_id="blabla",
            properties={"$session_id": 1},
            timestamp="2020-01-01 00:06:30",
        )
        _create_event(
            team=self.team,
            event="sign up",
            distinct_id="blabla",
            properties={"$session_id": 1},
            timestamp="2020-01-01 00:06:34",
        )
        _create_event(
            team=self.team,
            event="sign up later",
            distinct_id="blabla",
            properties={"$session_id": 1},
            timestamp="2020-01-01 00:06:35",
        )
        
        _create_event(