policy: add policy-integrity to mitigate policy tampering

PR-URL: https://github.com/nodejs/node/pull/28734


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>