## 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/trends/total_volume.py
def _parse(result: List) -> List:
            aggregated_value = ensure_value_is_json_serializable(result[0][0]) if result and len(result) else 0
            seconds_in_interval = TIME_IN_SECONDS[filter.interval]
            time_range = enumerate_time_range(filter, seconds_in_interval)
            filter_params = filter.to_params()
            extra_params = {
                "entity_id": entity.id,
                "entity_type": entity.type,
                "entity_math": entity.math,
                "entity_order": entity.order,
            }
            parsed_params: Dict[str, str] = encode_get_request_params({**filter_params, **extra_params})
            return [
                {
                    "aggregated_value": aggregated_value,
                    "days": time_range,
                    "filter": filter_params,
                    "persons": {
                        "filter": extra_params,
                        "url": f"api/projects/{team_id}/persons/trends/?{urllib.parse.urlencode(parsed_params)}",
                    },
                }
            ]
        return _parse
    def _get_persons_url(