ref(grouping): Consolidate main exception id override logic (#97541)

This is a small refactor to pull all the logic for overriding the `main_exception_id` event property into one place.

Author: lobsterkatie

src/sentry/grouping/strategies/newstyle.py

@@ -639,11 +639,9 @@ def chained_exception(
     # exceptions. Either way, we need to wrap our exception components in a chained exception component.
     exception_components_by_variant: dict[str, list[ExceptionGroupingComponent]] = {}
 
-    # Check for cases in which we want to switch the `main_exception_id` in order to use a different
+    # Handle cases in which we want to switch the `main_exception_id` in order to use a different
     # exception than normal for the event title
-    main_exception_id = determine_main_exception_id(exceptions)
-    if main_exception_id:
-        event.data["main_exception_id"] = main_exception_id
+    _maybe_override_main_exception_id(event, exceptions)
 
     for exception in exceptions:
         for variant_name, component in exception_components_by_exception[id(exception)].items():
@@ -897,11 +895,12 @@ def react_error_with_cause(exceptions: list[SingleException]) -> int | None:
 ]
 
 
-def determine_main_exception_id(exceptions: list[SingleException]) -> int | None:
+def _maybe_override_main_exception_id(event: Event, exceptions: list[SingleException]) -> None:
     main_exception_id = None
     for func in MAIN_EXCEPTION_ID_FUNCS:
         main_exception_id = func(exceptions)
         if main_exception_id is not None:
             break
 
-    return main_exception_id
+    if main_exception_id:
+        event.data["main_exception_id"] = main_exception_id