Time-window aggregation - Fix Nezha labeling

[mmantyla]

There is need to be able to aggregate logs based on a given size time window.

This will also fix the incorrect labeling that is currently in Nezha loader. Although Nezha datafiles also give hints on how they should be aggregated
https://github.com/EvoTestOps/LogLead/blob/main/loglead/loaders/nezha.py