src: move `ToUSVString()` to node_util.cc

Since `toUSVString()` was exposed in `util` as a public API, not only
for internal `url` any more.

PR-URL: https://github.com/nodejs/node/pull/40204


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>