test: allow leaked global check to be skipped

This simplifies the process of running tests on different
versions of Node, which might have a different set of
global variables.

PR-URL: https://github.com/nodejs/node/pull/27239


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>