## 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/trends/total_volume.py
if filter.display in NON_TIME_SERIES_DISPLAY_TYPES:
            if entity.math in PROPERTY_MATH_FUNCTIONS and entity.math_property == "$session_duration":
                
                
                content_sql = SESSION_DURATION_AGGREGATE_SQL.format(event_query=event_query, **content_sql_params)
            elif entity.math in COUNT_PER_ACTOR_MATH_FUNCTIONS:
                content_sql = VOLUME_PER_ACTOR_AGGREGATE_SQL.format(
                    event_query=event_query,
                    **content_sql_params,
                    aggregator="distinct_id" if team.aggregate_users_by_distinct_id else "person_id",
                )
            else:
                content_sql = VOLUME_AGGREGATE_SQL.format(event_query=event_query, **content_sql_params)
            return (content_sql, params, self._parse_aggregate_volume_result(filter, entity, team.id))
        else:
            if entity.math in [WEEKLY_ACTIVE, MONTHLY_ACTIVE]:
                content_sql = ACTIVE_USERS_SQL.format(
                    event_query=event_query,
                    **content_sql_params,
                    parsed_date_to=trend_event_query.parsed_date_to,
                    parsed_date_from=trend_event_query.parsed_date_from,
                    aggregator="distinct_id" if team.aggregate_users_by_distinct_id else "person_id",
                    start_of_week_fix=start_of_week_fix(filter.interval),
                    **trend_event_query.active_user_params,
                )
            elif filter.display == TRENDS_CUMULATIVE and entity.math == UNIQUE_USERS:
                
                cumulative_sql = CUMULATIVE_SQL.format(event_query=event_query)
                content_sql = VOLUME_SQL.format(
                    event_query=cumulative_sql,