fs: move `ToNamespacedPath` to c++

[anonrig]

This is a step forward to move all node:fs implementation to C++. Since we now have support for win32.pathResolve() in C++, we can move forward with moving ToNamespacedPath functions to C++.

In a follow up pull-request, I'll move FromNamespacedPath() from node_url.cc to path.cc

cc @nodejs/fs @RafaelGSS