process: move deprecation warning initialization into pre_execution.js

Since this is only necessary when user code execution is expected.

PR-URL: https://github.com/nodejs/node/pull/25825


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>