src: add public API for linked bindings

(Re-?)add a public API for creating linked bindings (access to
`NM_F_LINKED` as a constant was previously removed in
d6ac8a4d), and add a test for
the functionality.

PR-URL: https://github.com/nodejs/node/pull/26457


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>