util: use V8 C++ API for inspecting Promises

PR-URL: https://github.com/nodejs/node/pull/12254
Refs: https://github.com/nodejs/node/issues/11875


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Josh Gavant <josh.gavant@outlook.com>