child_process: restore exec{File}Sync error props

In PR [1], a bunch of properties were removed from the error thrown by
execSync and execFileSync. It turns out that some of those were still
supposed to be there, as the documentation states that the error
contains the entire result from the spawnSync call.

[1] https://github.com/nodejs/node/pull/13601

PR-URL: https://github.com/nodejs/node/pull/16060


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>