deps: re land npm 5.6.0

When the original backport was landed there were some missing commits
on v8.x. This commit completely re lands npm 5.6.0 to make sure the
version on 8.x has the correct file tree

Refs: https://github.com/nodejs/node/pull/16509#issuecomment-363410708
PR-URL: https://github.com/nodejs/node/pull/18625


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>