src: make AtExit() callbacks run in reverse order

This makes the actual behaviour match the documented (and arguably
the correct) behaviour.

PR-URL: https://github.com/nodejs/node/pull/30230


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>