Improve the performance of package json reader

[anonrig]

It's possible to improve the performance of loaders by:

• Reducing the data returned from c++/js
• Parse JSON on C++ side, instead of JSON.parse in JS
• Remove unnecessary caches on CJS

I've started and done most of the work, but soon I'll leave for the paternity leave and can not complete it.

Ref: nodejs/node#47991

[anonrig]

The performance impact of this task is really low. I'll close the issue for now.