Reconsider removing v5 & v6

@nechvatalp @nechvatalp Please reconsider how you all have restructured this library. It just broke a ton of our stuff with removing v6 & v5 code. In the old structure the various versions lived side-by-side so I think it's a fair assumption that people used liberal version restrictions assuming that the library would follow that pattern and not suddenly drop v6 from the code entirely.

未指定文件、测试或入口点。审查移除了 v5 和 v6 代码的重构，然后确定是否可以在不破坏现有版本限制的情况下恢复并列版本支持；完成意味着已确定兼容性方案及相应的实现范围。