[Error] ExceptionCatcher no more trace a message internally.
- Add ExceptionCatcher/ExceptionPtr::TracingMessage().
- Add polymorphic ExceptionHolder of Caramel::Exception and AnyFailure.
[Error] Change ExceptionPtr::Rethrow() to be const.
[Task] Task::Wait() and GetResult() throw exceptions if the task is faulted.
- This time it is implemented by ExceptionPtr.