Add hash index to speed up searching

[LianYangCn]

1. This patch allows you to boost searching from O(n) to O(1)
2. Because the implementation is based on the hash, it has to take more memory to store the index data.
3. And each key-value entry takes 4 bytes.
4. More details please reference the "Demos/Linux"

[LianYangCn]

各位大佬们，出来围观吊打我吧

[armink]

感谢你的 PR，这两天有些忙，我要晚点看下哈

[LianYangCn]

准备投入实际使用了

[armink]

👍， 我 十一 的时候再把整体框架梳理一下，后续 索引算法 应该会独立文件出来