MBS-13675: Split statistic events into history translation component

[reosarevok]

Implement MBS-13675

Description

History events (used in the history page and the timeline) are completely different from most statistics, and it seems sensible to translate them separately. In many cases, they probably are even less important than the rest of the statistics strings.

Testing

Tested manually that both history and timeline pages load. I'm not sure how to be entirely sure that the timeline is getting the translations from history and not statistics though.

Notes

Some changes might be overkill - I was trying to mostly follow l_statistics but it's likely some things I added for l_history are not actually needed yet.

I copied the events into the history .po files with:

#!/bin/bash
for filename in statistics.*.po; do
    output=${filename/statistics/history}
    msggrep $filename -N DB:statistics.statistic_event/* -o $output
done