src: add missing `NODE_WANT_INTERNALS` guards

We generally add these to all headers that are considered
internal to Node.

These aren’t distributed as part of the headers tarball,
so I think this does not have to be semver-major
(and we have been changing the APIs in these headers
freely anyway).

PR-URL: https://github.com/nodejs/node/pull/22514


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