When run apply_to_state_machine or append_to_log failed. How should to do

[bartliu827]

When an error occurs in those callback, openraft will exit the main loop, causing the program not run correctly; How to solve this situation.

[drmingdrmer]

If it is a storage error, e.g., data corruption, it should return an "StorageError" to inform Openraft to shutdown at once.

If it's an application error, the error should be wrapped in the Response, i.e., in this case, Response should be a Result<T, E>.

async fn apply_to_state_machine(
        &mut self,
        entries: &[Entry<TypeConfig>],
    ) -> Result<Vec<Response>, StorageError<NodeId>>