src: remove usage of V8 deprecated API in node_url.cc

Also:

- Avoid using 'override' as variable name
- Use explicit static_cast instead of C-style cast

PR-URL: https://github.com/nodejs/node/pull/11066


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>