test: add fs.watchFile() + worker.terminate() test

Refs: https://github.com/nodejs/node/pull/21093#discussion_r193563156

PR-URL: https://github.com/nodejs/node/pull/21179


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: James M Snell <jasnell@gmail.com>