Add game length percentile to match history data

[francislavoie]

In w3champions/website#889 we added duration bars to the match history pages:

These are currently linear scale up to a 30min maximum, as a "good enough" measurement.

What would be more accurate is to use the Game Lengths stats data we have, and add the game length percentile based on the game mode, to the match history data. This would make the bars more accurate to the mode's typical game lengths rather than being an educated guess.

If this would affect backend performance negatively, then we shouldn't do it. But if it's pretty easy to keep fast (caching the percentile buckets etc) then it should be okay to add. Will also need a subjective look to see if it actually improves the look of the bars, it might just not be any better.