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

En el issue no se identifican archivos de implementación ni pruebas. Empieza leyendo las dos discusiones de Node.js enlazadas y el contexto existente de la API crypto.Hash; el trabajo estará terminado cuando una operación de restablecimiento permita reutilizar un objeto Hash para nuevas asignaciones, conservando resultados de hash separados.