Add ability to subclass `stream.Duplex` without inheriting the
"no-half-open enforcer" regardless of the value of the `allowHalfOpen`
option.
PR-URL: https://github.com/nodejs/node/pull/18974
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Chen Gang <gangc.cxy@foxmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
