src: forbid handle allocations from Platform tasks

Platform tasks should have their own handle scopes, rather than
leak into outer ones.

PR-URL: https://github.com/nodejs/node/pull/26376


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>