feat: Improve robust score rendering with event-based architecture

This commit implements a comprehensive solution for test score integration in the
enhancement system along with improvements to the score rendering mechanism. Key
changes include:

- Add event handler for rendering blocks with edx-submissions scores
- Implement event-based mechanism to render XBlocks with scoring data
- Create signal handlers in handlers.py to process external grader scores
- Develop specialized XBlock loader for rendering without HTTP requests
- Add queue_key propagation across the submission pipeline
- Register submission URLs in LMS routing configuration
- Add complete docstrings to score render module for better code maintainability
- Add ADR for XBlock rendering with external grader integration
- Add openedx-events fork branch as a dependency in testing.in
- Upgrade edx submission dependency

These changes support the migration from traditional XQueue callback HTTP requests
to a more robust event-based architecture, improving performance and reliability
when processing submission scores. The included ADR documents the architectural
decision and implementation approach for this significant improvement to the
external grading workflow.

xmodule/capa/xqueue_interface.py

@@ -183,10 +183,12 @@ class XQueueInterface:
             return self._http_post(self.url + "/xqueue/submit/", payload, files=files)
 
         course_key = self.block.scope_ids.usage_id.context_key
+        header_info = json.loads(header)
+        queue_key = header_info['lms_key']
 
         if use_edx_submissions_for_xqueue(course_key):
-            submission = self.submission.send_to_submission(header, body, files)
-            return None, ""
+            submission = self.submission.send_to_submission(header, body, queue_key, files)
+            return None, ''
 
         return self._http_post(self.url + "/xqueue/submit/", payload, files=files)