test: add test for cluster benchmarks

Add minimal test to make sure cluster benchmark code runs.

PR-URL: https://github.com/nodejs/node/pull/14812


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>