## 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/breakdown.py
if self.filter.breakdown_type == "session":
            if breakdown == "$session_duration":
                
                
                breakdown_value = f"{SessionQuery.SESSION_TABLE_ALIAS}.session_duration"
            else:
                raise ValidationError(f'Invalid breakdown "{breakdown}" for breakdown type "session"')
        elif (
            self.using_person_on_events
            and self.filter.breakdown_type == "group"
            and groups_on_events_querying_enabled()
        ):
            properties_field = f"group{self.filter.breakdown_group_type_index}_properties"
            breakdown_value, _ = get_property_string_expr(
                "events", breakdown, "%(key)s", properties_field, materialised_table_column=properties_field
            )
        elif self.using_person_on_events and self.filter.breakdown_type != "group":
            if self.filter.breakdown_type == "person":
                breakdown_value, _ = get_property_string_expr(
                    "events", breakdown, "%(key)s", "person_properties", materialised_table_column="person_properties"
                )
            else:
                breakdown_value, _ = get_property_string_expr("events", breakdown, "%(key)s", "properties")
        else:
            if self.filter.breakdown_type == "person":
                breakdown_value, _ = get_property_string_expr("person", breakdown, "%(key)s", "person_props")
            elif self.filter.breakdown_type == "group":
                properties_field = f"group_properties_{self.filter.breakdown_group_type_index}"
                breakdown_value, _ = get_property_string_expr(
                    "groups", breakdown, "%(key)s", properties_field, materialised_table_column="group_properties"