## 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
"value_at_data_point": 1,  # 
                },
                {
                    "created_at": "2020-01-01T12:00:00Z",
                    "distinct_ids": ["person3"],
                    "id": str(person3.uuid),
                    "is_identified": False,
                    "matched_recordings": [],
                    "name": "person3",
                    "properties": {},
                    "type": "person",
                    "uuid": str(person3.uuid),
                    "value_at_data_point": 1,  # 
                },
            ]
            people_value_2 = self._get_trend_people(Filter(data={**data, "breakdown_value": "value_2"}), entity)
            assert people_value_2 == [
                {
                    "created_at": "2020-01-01T12:00:00Z",
                    "distinct_ids": ["person2"],
                    "id": str(person2.uuid),
                    "is_identified": False,
                    "matched_recordings": [],
                    "name": "person2",
                    "properties": {},
                    "type": "person",
                    "uuid": str(person2.uuid),
                    "value_at_data_point": 1,  # 
                }
            ]