add a new getter to duplex stream to replace the property `this
.writableState.finished` of the object that inherited duplex.
Refs: https://github.com/nodejs/node/issues/445
PR-URL: https://github.com/nodejs/node/pull/28007
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
