worker: reduce `MessagePort` prototype to documented API

`MessagePort` is special because it has to be a C++ API
that is exposed to userland. Therefore, there is a number
of internal methods on its native prototype; this commit
reduces this set of methods to only what is documented in
the API.

PR-URL: https://github.com/nodejs/node/pull/23037


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>