Implement the ability to select a time cutoff for the leaderboard

[wctaiwan]

The current win ratio ranking is probably a skewed representation, as the modes have evolved quite a bit since stats started being collected on the Libera instance. For example, even though the minimum player count has been 6 for a long time, 4p games are still by far the most numerous (from today: Total games (default): 13475 | 4p: 5262, 5p: 2560, 6p: 2067, 7p: 696, 8p: 691, 9p: 876, 10p: 576, 11p: 307, 12p: 188, 13p: 109, 14p: 60, 15p: 38, 16p: 25, 17p: 11, 18p: 5, 19p: 1, 20p: 2, 24p: 1), so players who have been playing for a long time probably have a pretty different mix of games making up their stats compared to newer players, making the relative win ratio less meaningful.

One way to mitigate this would be to implement a way for the user to select a time cutoff for the leaderboard columns. By default it can factor in only recent games, with the all time stats still being viewable if explicitly selected.