Handle errors when failing to send tracked messages

[TylerBloom]

Currently, the code for sending a tracked message to an actor ignores failures on send. This will still cause the tracker to yield a None, but that will occur only after the tracker is polled. For clients sending a message to a Permanent actor, this message could be unwrapped in the track call to provide a clearer error message. There isn't a clear solution for sending messages to Transient actors. Perhaps an option-like enum can be used? Maybe nothing at all is needed?