bindings/rust: Fix Rows::next() I/O dispatcher handling

The `next()` function needs to be a loop to make sure we actually return rows.

bindings/rust/tests/integration_tests.rs

@@ -0,0 +1,27 @@
+use limbo::Builder;
+
+#[tokio::test]
+async fn test_rows_next() {
+    let builder = Builder::new_local(":memory:");
+    let db = builder.build().await.unwrap();
+    let conn = db.connect().unwrap();
+    conn.execute("CREATE TABLE test (x INTEGER)", ())
+        .await
+        .unwrap();
+    conn.execute("INSERT INTO test (x) VALUES (1)", ())
+        .await
+        .unwrap();
+    conn.execute("INSERT INTO test (x) VALUES (2)", ())
+        .await
+        .unwrap();
+    let mut res = conn.query("SELECT * FROM test", ()).await.unwrap();
+    assert_eq!(
+        res.next().await.unwrap().unwrap().get_value(0).unwrap(),
+        1.into()
+    );
+    assert_eq!(
+        res.next().await.unwrap().unwrap().get_value(0).unwrap(),
+        2.into()
+    );
+    assert!(res.next().await.unwrap().is_none());
+}