Enable Fill on the timeGroup macro

[CraigLager]

Is your feature request related to a problem? Please describe.

Timeseries graphs using the redshift $__timeGroup macro are incorrect as groups with no data are not filled in. For example, the query:

SELECT
    $__timeGroup(timestamp, '10m'),
    count($__column)
FROM 
    $__schema.$__table
WHERE
    $__timeFilter(timestamp)
    and $__column = '$Seller'
GROUP BY
    time
ORDER BY
    time

Results in:

time	count
2025-01-15 14:00	1
2025-01-15 14:10	1
2025-01-15 14:30	1
2025-01-15 14:40	1
2025-01-15 15:00	1
2025-01-15 15:20	1
2025-01-15 15:30	1
2025-01-15 15:40	2
2025-01-15 16:10	2
2025-01-15 16:40	1
2025-01-15 16:50	3
2025-01-15 17:00	1
2025-01-16 05:00	1
2025-01-16 06:00	2

Notice the gap at 14:20, 14:50 etc. As there is no row, the grafana Fill options don't do anything. This results in timeseries graphs being incorrect

Describe the solution you'd like

Rows should be generated and the value returned as NULL for missing entries in the time group.

Describe alternatives you've considered

Creating a data source which is just timestamps to left join

Additional context

Postgres has support for this feature: https://grafana.com/docs/grafana/latest/datasources/postgres/#macros