vm: mark global proxy as side-effect-free

Fixes: https://github.com/nodejs/node/issues/27518

PR-URL: https://github.com/nodejs/node/pull/27523


Reviewed-By: Aleksei Koziatinskii <ak239spb@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>