use kahan for avg_over_time
use kahan for avg_over_time

Signed-off-by: darshanime <b048a3d8d104e53464fdce5e113778ad2e9730e1@gmail.com>

alileza/prometheus,prometheus/prometheus,keegancsmith/prometheus,prometheus/prometheus,keegancsmith/prometheus,alileza/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,keegancsmith/prometheus,alileza/prometheus,alileza/prometheus,alileza/prometheus