util: adding warnings when NODE_DEBUG is set as http/http2

PR-URL: https://github.com/nodejs/node/pull/21914


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>