worker: refactor MessagePort entanglement management

This addresses the `TODO` left on my request in 9e446b3e. :)

Refs: https://github.com/nodejs/node/pull/36271

PR-URL: https://github.com/nodejs/node/pull/36345


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>