Bug 1865633 - Reset the stream when it's not usable, r=necko-reviewers,valentin

Depends on D194083

Differential Revision: https://phabricator.services.mozilla.com/D194084

netwerk/test/http3server/src/main.rs

@@ -708,7 +708,8 @@ impl Http3ProxyServer {
                 }
             }
             Err(e) => {
-                eprintln!("error is {:?}", e);
+                eprintln!("error is {:?}, stream will be reset", e);
+                let _ = stream.stream_reset_send(Error::HttpRequestCancelled.code());
             }
         }
     }