Support __range_s variable in the Loki query editor.

[wardbekker]

Like with Prometheus, upcoming Loki topK queries need the correct range to return the expected number of results. $__interval is supported, but this returns more results than the limit set in the topK, which is correct but counter-intuitive and not what is needed by the user. See also the Prometheus docs here:
https://grafana.com/docs/grafana/latest/features/datasources/prometheus/#templating

Loki is going to support the following syntax in upcoming versions:

topk(5, sum by (ipaddress) (count_over_time({filename="/var/log/nginx/access.log"} | regexp "(?P\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})"[10m])))

[candux]

I also wrestled with this problem for some time.
One workaround is to set "Max date points" in the Query Options to 1.
Then $__interval is always equal to what would be $__range

[Phara0h]

Any updates on this bad boy?