Limit stacktrace to check performance impact

pyfakefs/helpers.py

@@ -446,7 +446,7 @@ def starts_with(path, string):
             return path.startswith(string)
         return path.lower().startswith(string.lower())
 
-    stack = traceback.extract_stack()
+    stack = traceback.extract_stack(limit=6)
 
     # handle the case that we try to call the original `open_code`
     # (since Python 3.12)