bpo-45662: Fix the repr of InitVar with a type alias to the built-in class (GH-29291)


For example, InitVar[list[int]].
(cherry picked from commit 1fd4de5bddbbf2a97cdbac4d298c89e1156bdc6c)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index bcd004f..47075df 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -1126,6 +1126,10 @@ def test_init_var_preserve_type(self):
         self.assertEqual(repr(InitVar[int]), 'dataclasses.InitVar[int]')
         self.assertEqual(repr(InitVar[List[int]]),
                          'dataclasses.InitVar[typing.List[int]]')
+        self.assertEqual(repr(InitVar[list[int]]),
+                         'dataclasses.InitVar[list[int]]')
+        self.assertEqual(repr(InitVar[int|str]),
+                         'dataclasses.InitVar[int | str]')
 
     def test_init_var_inheritance(self):
         # Note that this deliberately tests that a dataclass need not