process: runtime deprecate changing process.config

The fact that `process.config` is mutable has long made it
unreliable when it really should just work. Start the process
of deprecating the ability to change it.

Fixes: https://github.com/nodejs/node/issues/7803


Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/36902


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>