test: move common.onGC to individual module

Incrementally making `require('../common')` less of a monolith.
Move the `common.onGC()` utility to a separate standalone module
that is only imported when it's actually needed.

PR-URL: https://github.com/nodejs/node/pull/22446


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>