logging: Report stack_info on logging.exception calls.

The exception trace only goes from where the exception was thrown up
to where the `logging.exception` call is; any context as to where
_that_ was called from is lost, unless `stack_info` is passed as well.
Having the stack is particularly useful for Sentry exceptions, which
gain the full stack trace.

Add `stack_info=True` on all `logging.exception` calls with a
non-trivial stack; we omit `wsgi.py`.  Adjusts tests to match.

zerver/management/commands/runtornado.py

@@ -34,7 +34,7 @@ if settings.USING_RABBITMQ:
 
 
 def handle_callback_exception(callback: Callable[..., Any]) -> None:
-    logging.exception("Exception in callback")
+    logging.exception("Exception in callback", stack_info=True)
     app_log.error("Exception in callback %r", callback, exc_info=True)
 
 class Command(BaseCommand):