feat: scaffold streaming e2e fixtures

crates/crank-adapter-grpc/examples/stream_fixture.rs

@@ -0,0 +1,22 @@
+use crank_adapter_grpc::test_support::{EchoServiceImpl, echo};
+use tokio::net::TcpListener;
+use tonic::transport::Server;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let bind = std::env::var("CRANK_E2E_GRPC_FIXTURE_BIND")
+        .unwrap_or_else(|_| "127.0.0.1:3311".to_owned());
+    let listener = TcpListener::bind(&bind).await?;
+    let incoming = tonic::transport::server::TcpIncoming::from(listener);
+
+    println!("gRPC stream fixture listening on http://{bind}");
+
+    Server::builder()
+        .add_service(echo::echo_service_server::EchoServiceServer::new(
+            EchoServiceImpl,
+        ))
+        .serve_with_incoming(incoming)
+        .await?;
+
+    Ok(())
+}