Improve error message when exception is not caught in orchestrator

[davidmrdavid]

If we raise an exception in an activity function, it is not serialized by the language worker. We need it to be serialized and re-thrown in the orchestrator for the correct experience around try-catch'ed activites.

[davidmrdavid]

I believe this an error that needs to be addressed at the worker level. @Hazhzeng any chance you could lend me a hand on this?

[davidmrdavid]

I take it back, exceptions are serializable. However, when an end-user fails to wrap an exception-throwing activity in a try-catch block, the status of their orchestration throws a non-intuitive error reading: reference not set to instance of an object. We should improve this

[davidmrdavid]

Another related error. If we raise an error at the final line of the orchestrator's handle method, it gets swallowed and the orchestrator appears to succeed.