* [Java] [Native] Unify exception messages for async, add the status code
The template has two methods for creating API exceptions, and the enhancements from #9169 didn't make it to the async version.
- unify the signatures of the two methods (name, arguments)
- make sure the sync version is not generated with asyncNative
- extract the formatting logic into a common formatExceptionMessage() method
- add the status code to the exception message as well, not just the body
- shortened "call received non-success response" to a more concise "call failed with"
* Treat an empty body the same as a null body
Co-authored-by: Jens Fischer <jens.fischer@vier.ai>