esm: ensure require.main for CJS top-level loads

PR-URL: https://github.com/nodejs/node/pull/21150


Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>