## 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/util.py
join_condition = ""
    params: Dict[str, Any] = {}
    if entity.math == UNIQUE_USERS:
        if team.aggregate_users_by_distinct_id:
            join_condition = ""
            aggregate_operation = f"count(DISTINCT {event_table_alias + '.' if event_table_alias else ''}distinct_id)"
        else:
            join_condition = EVENT_JOIN_PERSON_SQL
            aggregate_operation = f"count(DISTINCT {person_id_alias})"
    elif entity.math == "unique_group":
        validate_group_type_index("math_group_type_index", entity.math_group_type_index, required=True)
        aggregate_operation = f'count(DISTINCT "$group_{entity.math_group_type_index}")'
    elif entity.math == "unique_session":
        aggregate_operation = f"count(DISTINCT {event_table_alias + '.' if event_table_alias else ''}\"$session_id\")"
    elif entity.math in PROPERTY_MATH_FUNCTIONS:
        if entity.math_property is None:
            raise ValidationError(
                {"math_property": "This field is required when `math` is set to a function."}, code="required"
            )
        if entity.math_property == "$session_duration":
            aggregate_operation = f"{PROPERTY_MATH_FUNCTIONS[entity.math]}(session_duration)"
        else:
            key = f"e_{entity.index}_math_prop"
            value, _ = get_property_string_expr("events", entity.math_property, f"%({key})s", "properties")
            aggregate_operation = f"{PROPERTY_MATH_FUNCTIONS[entity.math]}(toFloat64OrNull({value}))"
            params[key] = entity.math_property
    elif entity.math in COUNT_PER_ACTOR_MATH_FUNCTIONS:
        aggregate_operation = f"{COUNT_PER_ACTOR_MATH_FUNCTIONS[entity.math]}(intermediate_count)"
    return aggregate_operation, join_condition, params
def parse_response(stats: Dict, filter: Filter, additional_values: Dict = {}) -> Dict[str, Any]: