Allow Hash object reuse

What is the problem this feature will solve?

https://github.com/nodejs/node/issues/25857#issuecomment-466384613

I'm creating the hash of many small objects and need to keep track of these individual hashes so https://github.com/nodejs/node/issues/29903 doesn't work.

My specific use case is that I'm hashing directory layouts to setup a file layout that's optimal about symlinking entire directories when its filled with symlinked entries that all point to the same source directory. I can get into specifics if that matters.

What is the feature you are proposing to solve the problem?

crypto.Hash.reset() - reset the internal state of the hasher and allows it to be reused with any new allocations

What alternatives have you considered?

-not use crypto.hash in this case and write my own hasher
-create a native add on that lets me manage to hash context according to my needs

Issue 中没有指出实现文件或测试。首先阅读链接的两篇 Node.js 讨论以及现有的 crypto.Hash API 上下文；完成的标准是，reset 操作可以让一个 Hash 对象用于新的分配，同时保留彼此独立的哈希结果。