### Check existing issues - [x] I've verified that this request isn't described by any existing issues. ### Request Return different error codes based on the store response from `snapcraft upload`: - `ready_to_release` -> 0 - `being_processed` -> ? - `need_manual_review` -> ? - `processing_upload_delta_error` -> ? - `processing_error` -> ? - all other errors unrelated to the store response -> 1 The error codes should be added to the command's reference documentation. The implementation should be as straightforward as getting `status[code]` and raising the appropriate error code [here](https://github.com/canonical/snapcraft/blob/603626051f05b64f19b683fc3d5ea3edca1b8628/snapcraft/store/client.py#L471-L478). ### The problem it solves This allows CI workflows to programmatically handle the result of `snapcraft upload`. Fixes #6076