Implement a log rotation every N benchmarks

We should cut the data files in N elements so that the website do not load a million results and try to render it all at once.

Files could be stored as (i*N)-original-name, so that we can find them easily.

We should also limit the number of elements in the current file to N max. All the excess should go to another file (N*i)-original-name.

The old files will then file up slowly and we will still have enough data in the current files for the graphs.

该 issue 没有列出文件或测试。首先定位 benchmark 数据 writer 以及读取这些文件的 website 代码，然后跟踪当前文件是如何追加的，以及图表所需的结果是如何加载的。完成标准是：文件会按照可配置的 N 个元素上限进行拆分，并且 website 仍然能够找到并渲染已存储的 benchmark 数据。

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