feat: Enhance Server::new to accept impl Into<Option<Opt>> for ergonomics

[gengteng]

This PR simplifies the Server::new function interface by allowing direct passing of Opt or None without the need to wrap with Some. This enhancement makes the API more ergonomic and user-friendly.

Changes:

• Before: Required to wrap Opt with Some.

let my_server = Server::new(Some(Opt::from_args())).unwrap();

• After: Direct passing of Opt or None.

let my_server = Server::new(Opt::from_args()).unwrap();
let my_server = Server::new(None).unwrap();

// The previous method of wrapping `Opt` with `Some` is still supported.
let my_server = Server::new(Some(Opt::from_args())).unwrap();

This update streamlines function calls, improving the overall developer experience.