remove unecessary fs.stat calls from recursive-readdir (#27769)
remove unecessary fs.stat calls from recursive-readdir (#27769)

## Performance improvement

- [x] Performance improvement

Removes unnecessary `fs.stat` calls in `recursiveReadDir`.

`fs.readdir` had an option `withFileTypes: boolean` added NodeJS version 10. It can be used to read the directory contents and fetch its stats simultaneously, removing the need to read individual file stats after reading the directory contents.
JeromeFitz/next.js,azukaru/next.js,azukaru/next.js,zeit/next.js,JeromeFitz/next.js,JeromeFitz/next.js,flybayer/next.js,flybayer/next.js,azukaru/next.js,flybayer/next.js,zeit/next.js,azukaru/next.js,zeit/next.js,flybayer/next.js,JeromeFitz/next.js