Built-in retry mechanism in GET requests in sdk using HttpUrlConnection

- Do you think we should add the retry thing for all the methods? I can do that as part of this ticket.
- If you plan to delete the async tasks, why should we fix them first?
- I'm not sure we should delete the async tasks, as most API provide a blocking API. I would just make them use the blocking API. I don't think the official app will use most of them anyway.