Pass course-run-specific resource limits to codejail

The limits can be defined in settings.CODE_JAIL['limits_overrides'],
which is a dict mapping context ids (generally, course run keys)
to overrides to be applied to settings.CODE_JAIL['limits'].

This will allow us to temporarily alter the codejail limits
for certain contexts in order to enable, for example,
a certain course run's tasks to run longer while a large exam's
grades are recomputed.

TNL-7649

lms/djangoapps/debug/views.py

@@ -17,7 +17,14 @@ from openedx.core.djangolib.markup import HTML
 @login_required
 @ensure_csrf_cookie
 def run_python(request):
-    """A page to allow testing the Python sandbox on a production server."""
+    """
+    A page to allow testing the Python sandbox on a production server.
+
+    Runs in the override context "debug_run_python", so resource limits with come first from:
+        CODE_JAIL['limit_overrides']['debug_run_python']
+    and then from:
+        CODE_JAIL['limits']
+    """
     if not request.user.is_staff:
         raise Http404
     c = {}
@@ -27,7 +34,7 @@ def run_python(request):
         py_code = c['code'] = request.POST.get('code')
         g = {}
         try:
-            safe_exec(py_code, g)
+            safe_exec(py_code, g, limit_overrides_context="debug_run_python")
         except Exception:   # pylint: disable=broad-except
             c['results'] = traceback.format_exc()
         else: