test: add more settings to test-benchmark-dgram

Add settings to test-benchmark-dgram such that it only runs benchmark
per benchmark file.

PR-URL: https://github.com/nodejs/node/pull/17462


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>