[dynamo][easy] support sys.intern (pytorch#136081)

Closes pytorch#134023

- pytorch#134023

Pull Request resolved: pytorch#136081
Approved by: https://github.com/anijain2305

torch/_dynamo/polyfills/sys.py

@@ -2,5 +2,18 @@
 Python polyfills for sys
 """
 
+from __future__ import annotations
 
-__all__ = []  # type: ignore[var-annotated]
+import sys
+
+from ..decorators import substitute_in_graph
+
+
+__all__ = [
+    "intern",
+]
+
+
+@substitute_in_graph(sys.intern, can_constant_fold_through=True)
+def intern(string: str, /) -> str:
+    return string