Feature request: send proto upgrade `Response` from handler.

The upgrade example from 1.0.0-rc.3 looks odd (in my opinion).

In web socket context, If the server decides to upgrade the connection, It just send a 101 Switching Protocols response, and immediately use internal TCP as WebSocket protocol.

No need for extra task::spawn:
https://github.com/hyperium/hyper/blob/9ed175d1545fa338b6212c4f48be9b3d12821c7a/examples/upgrades.rs#L58-L59

Sure, Its only possible, If there is an option to write response directly (rather then returning writable Response object)

Maybe add such API ?

For example:

async handle(req: Request<Incoming>) -> Result<Response<..> {
    match hyper::upgrade::send_response_and_upgrade(resp_body, req).await {
        Err(msg) => eprintln!("upgrade error: {msg}"),
        Ok(upgraded) => { ... }
    }
}

Start with examples/upgrades.rs and the linked upgrade flow to understand why the extra task::spawn is used. Evaluate the proposed hyper::upgrade::send_response_and_upgrade API against the current handler response model. Done means a supported way to send the 101 response and obtain the upgraded connection directly, with the upgrade example reflecting the resulting flow.