cluster: add cwd to cluster.settings

This commit allows cluster workers to be created with
configurable working directories.

Fixes: https://github.com/nodejs/node/issues/16388
PR-URL: https://github.com/nodejs/node/pull/18399


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>