## 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)`.

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posthog/queries/test/test_trends.py
)
        data = {
            "date_from": "2020-01-08",
            "date_to": "2020-01-19",
            "actions": [{"id": action.id, "type": "actions", "order": 0, "math": "weekly_active"}],
        }
        filter = Filter(data=data)
        result = Trends().run(filter, self.team)
        # 
        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])
    @test_with_materialized_columns(["key"])
    def test_breakdown_weekly_active_users(self):
        _create_person(team_id=self.team.pk, distinct_ids=["p1"], properties={"name": "p1"})
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p1",
            timestamp="2020-01-09T12:00:00Z",
            properties={"key": "val"},
        )
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p1",
            timestamp="2020-01-10T12:00:00Z",
            properties={"key": "val"},
        )
        _create_event(
            team=self.team,
            event="$pageview",