Add .closed property to NamedTemporaryFile (#12349)

This is necessary for a NamedTemporaryFile to be compatible with io.TextIOWrapper.

stdlib/tempfile.pyi

@@ -264,6 +264,8 @@ class _TemporaryFileWrapper(IO[AnyStr]):
     def writelines(self: _TemporaryFileWrapper[bytes], lines: Iterable[ReadableBuffer]) -> None: ...
     @overload
     def writelines(self, lines: Iterable[AnyStr]) -> None: ...
+    @property
+    def closed(self) -> bool: ...
 
 if sys.version_info >= (3, 11):
     _SpooledTemporaryFileBase = io.IOBase