watch: reload changes in contents of --env-file
Make sure we watch and reload on env file changes. Ignore env file in parent process, so child process can reload current vars when we recreate it.
Fixes: https://github.com/nodejs/node/issues/54001
I've noticed now that it's probably a duplicate of https://github.com/nodejs/node/pull/54033.
Feel free to close or reuse tests from here in the other PR if you plan on merging it.
It was a nice small bug to get feet wet with Node internals anyway.