test: wait for uv.pipe_connect() callback (#37640)

Problem:
On Windows, writing to a pipe doesn't work if the pipe isn't connected
yet. This causes an RPC request to a session newly created by connect()
to hang, as it's waiting for a response to a request that never reaches
the server.

Solution:
Wait for uv.pipe_connect() callback to be called when using connect().

test/client/uv_stream.lua

@@ -67,8 +67,15 @@ function SocketStream.open(file)
     _stream_error = nil,
   }, SocketStream)
   uv.pipe_connect(socket, file, function(err)
+    uv.stop()
     self._stream_error = self._stream_error or err
   end)
+  -- On Windows, writing to the pipe doesn't work if it's not connected yet,
+  -- so wait for the connect callback to be called.
+  uv.run()
+  if self._stream_error then
+    error(self._stream_error)
+  end
   return self
 end