UI to show multiple stats for other users

**Is your feature request related to a problem? Please describe.**
I'd like to be able to see mean / ao5 / ao12 / etc... for other users at the same time

**Describe the solution you'd like**
One option is to press the "mean" button to cycle between the stats. This won't be obvious to most users however.

Another option is to press mean and it toggles more rows showing in the header with the various stats (if enough solves exist for any user)

Another option is to add a whole other panel and somehow toggle between viewing it.

首先定位在 header 中显示 mean 按钮和每个用户统计数据的 UI。查看现有的 solve 次数和统计数据是如何显示的，然后明确应选择哪种交互或 panel 设计；完成应意味着用户可以同时查看多个用户的 mean、ao5、ao12 以及其他可用统计数据。

由索引模型根据 Issue 内容生成。