child_process: fix stdio sockets creation

`readable` and `writable` properties can be passed directly to the
`net.Socket` constructor. This change also avoids an unnecessary call
to `read(0)` on the `stdin` socket. This behavior was disclosed when
trying to merge `libuv@1.19.0` and specifically this commit:
https://github.com/libuv/libuv/commit/fd049399aa4ed8495928e375466970d98cb42e17.

PR-URL: https://github.com/nodejs/node/pull/18701
Refs: https://github.com/libuv/libuv/pull/1655


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>