gh-138584: Increase test coverage for collections.UserList (#138590)

Some common tests in `test.list_tests.CommonTest` explicitly tested `list`
instead of testing the underlying list-like type defined in `type2test`.

---------

Co-authored-by: Devansh Baghla <[email protected]>

Author: dbXD320

Lib/test/list_tests.py

@@ -32,13 +32,13 @@ def test_init(self):
         self.assertEqual(a, b)
 
     def test_getitem_error(self):
-        a = []
+        a = self.type2test([])
         msg = "list indices must be integers or slices"
         with self.assertRaisesRegex(TypeError, msg):
             a['a']
 
     def test_setitem_error(self):
-        a = []
+        a = self.type2test([])
         msg = "list indices must be integers or slices"
         with self.assertRaisesRegex(TypeError, msg):
             a['a'] = "python"
@@ -561,7 +561,7 @@ def test_constructor_exception_handling(self):
         class F(object):
             def __iter__(self):
                 raise KeyboardInterrupt
-        self.assertRaises(KeyboardInterrupt, list, F())
+        self.assertRaises(KeyboardInterrupt, self.type2test, F())
 
     def test_exhausted_iterator(self):
         a = self.type2test([1, 2, 3])