process: avoid using the same fd for ipc and stdio

There is already a check in place to prevent stdin and the IPC
channel from sharing a file descriptor. This commit adds a
similar check to stdout and stderr.

Refs: https://github.com/libuv/libuv/pull/1851
Refs: https://github.com/libuv/libuv/issues/1897
PR-URL: https://github.com/nodejs/node/pull/21466


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>