src: clean up `node::Init()` wrt embedder scenarios

This makes the STL variant of `node::Init()` a bit more
suitable for inclusion in a proper embedder API, as errors
or other output are reported to the caller rather than
directly being printed, and the process is not exited
directly either.

PR-URL: https://github.com/nodejs/node/pull/25370


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>