child_process: treat already-aborted controller as aborting

If an AbortController passed to execfile() is already aborted, use the
same behavior as if the controller was aborted after calling execfile().
This mimics the behavior of fetch in the browser.

PR-URL: https://github.com/nodejs/node/pull/36644


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>