errors: make `code` and `name` properties settable

For internal errors, make `code` and `name` settable while keeping them
non-own properties by default.

PR-URL: https://github.com/nodejs/node/pull/15694
Fixes: https://github.com/nodejs/node/issues/15658


Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>