src: do not add .domain to promises in VM contexts

The promises are still tracked, and their handlers will still execute in
the correct domain. The creation domain is simply hidden.

PR-URL: https://github.com/nodejs/node/pull/15695
Fixes: https://github.com/nodejs/node/issues/15673


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>