## 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
"2020-01-09 17:00:00",
            ],
        )
        # 
        # 
        # 
        # 
        # 
        self.assertEqual(result[0]["data"], [3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0])
    def test_weekly_active_users_daily_based_on_action_with_zero_person_ids(self):
        
        if not get_instance_setting("PERSON_ON_EVENTS_ENABLED"):
            return True
        action = _create_action(name="$pageview", team=self.team)
        self._create_active_users_events()
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p5",
            timestamp="2020-01-03T12:00:00Z",
            properties={"key": "val"},
            person_id="00000000-0000-0000-0000-000000000000",
        )
        _create_event(
            team=self.team,
            event="$pageview",
            distinct_id="p6",
            timestamp="2020-01-03T12:00:00Z",
            properties={"key": "val"},
            person_id="00000000-0000-0000-0000-000000000000",