fix: run blocking function on a different task (#2570)

This avoids freezing the current task if the fn blocks indefinitely

cli/ops.rs

@@ -793,9 +793,10 @@ where
     let result_buf = f()?;
     Ok(Op::Sync(result_buf))
   } else {
-    Ok(Op::Async(Box::new(tokio_util::poll_fn(move || {
+    Ok(Op::Async(Box::new(futures::sync::oneshot::spawn(
-      convert_blocking(f)
+      tokio_util::poll_fn(move || convert_blocking(f)),
-    }))))
+      &tokio_executor::DefaultExecutor::current(),
+    ))))
   }
 }