src: prefer OnScopeLeave over shared_ptr<void>

They do the same thing, but OnScopeLeave avoids an extra
heap allocation and is more explicit about what it does.

PR-URL: https://github.com/nodejs/node/pull/32247


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>