src: use UTF-8 for naming interfaces in unix

Use a UTF-8 encoded string for naming interfaces in unix, instead of
using Latin-1, as had been done on windows previously.

PR-URL: https://github.com/nodejs/node/pull/21926


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>