src: use modern v8::Platform worker threads APIs

Precursor to removing deprecated APIs on the v8 side @
https://chromium-review.googlesource.com/c/v8/v8/+/1045310

PR-URL: https://github.com/nodejs/node/pull/21079


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yang Guo <yangguo@chromium.org>