## 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/sql.py
-- enumerate all requested periods, so we can zero fill as needed.
    -- NOTE: we use dateSub interval rather than seconds, which means we can handle,
    -- for instance, month intervals which do not have a fixed number of seconds.
    periods AS (
        SELECT dateSub(
            {{interval_expr}},
            number,
            dateTrunc(selected_period, toDateTime(%(date_to)s, %(timezone)s))
        ) AS start_of_period
        FROM numbers(
            dateDiff(
                %(interval)s,
                dateTrunc(%(interval)s, toDateTime(%(date_from)s, %(timezone)s)),
                dateTrunc(%(interval)s, toDateTime(%(date_to)s, %(timezone)s) + INTERVAL 1 {{interval_expr}})
            )
        )
    )
SELECT
    groupArray(start_of_period) as date,
    groupArray(counts) as data,
    status
FROM (
    SELECT if(
            status = 'dormant',
            toInt64(SUM(counts)) * toInt16(-1),
            toInt64(SUM(counts))
        ) as counts,
        start_of_period,
        status
    FROM (