src: enable non-nestable V8 platform tasks

We never execute tasks in a nested fashion, so enabling them should
be as simple as forwarding tasks to the existing `Post*` methods.

PR-URL: https://github.com/nodejs/node/pull/27252


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>