src: use option parser for expose_internals

bootstrap_node.js was directly parsing process.execArgv to see if
internals should be exposed, even though the argv was already parsed by
node. This is unusual and unnecessary, change it to set the option value
from the parser onto the config binding.

PR-URL: https://github.com/nodejs/node/pull/12245


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>