This commit adds new SerReceiver::try_cast and
DeserSender::try_cast methods, which attempt to recover a typed Receiver or Sender from an erased SerReceiver or DeserSender, respectively. These methods return an error if the requested type does not match the original erased type.
This commit adds new
SerReceiver::try_castandDeserSender::try_castmethods, which attempt to recover a typedReceiverorSenderfrom an erasedSerReceiverorDeserSender, respectively. These methods return an error if the requested type does not match the original erased type.