p3(http): `request.new` transmission future resolves to `ok` when `client.send` fails

Consider the following program:

```rust
use test_wasm32_wasip3::http::wasi::http::client;
use test_wasm32_wasip3::http::wasi::http::types::{
ErrorCode, Fields, Method, Request, Response, Scheme,
};
use test_wasm32_wasip3::http::wit_future;
use test_wasm32_wasip3::http::{export, exports::wasi::http::handler::Guest};

struct Component;
export!(Component);

impl Guest for Component {
async fn handle(_request: Request) -> Result {
let (trailers_tx, trailers_rx) = wit_future::new(|| Ok(None));
drop(trailers_tx);

let (request, sent) = Request::new(Fields::new(), None, trailers_rx, None);
request.set_method(&Method::Get).unwrap();
request.set_scheme(Some(&Scheme::Http)).unwrap();
request
.set_authority(Some("nonexistent.invalid:80"))
.unwrap();
request.set_path_with_query(Some("/")).unwrap();

client::send(request)
.await
.expect_err("send to an unresolvable authority should fail");
assert!(
sent.await.is_err(),
"a request that was never transmitted must not report successful transmission"
);

let (trailers_tx, trailers_rx) = wit_future::new(|| Ok(None));
drop(trailers_tx);
let (response, _sent) = Response::new(Fields::new(), None, trailers_rx);
response.set_status_code(200).unwrap();
Ok(response)
}
}

fn main() {
unreachable!("main is a stub");
}
```

It fails the following statement, using `wasmtime` `v46` and `main`:

```rust
assert!(
sent.await.is_err(),
"a request that was never transmitted must not report successful transmission"
);
```

#### Expected behavior

The spec for `request.new` [states](https://github.com/WebAssembly/WASI/blob/main/proposals/http/wit/types.wit#L307):

> The returned future resolves to result of transmission of this request

The returned future should resolve to an error, according to the spec.