bpo-44524: Do not set _name of _SpecialForm without need (GH-27861) (GH-27871)

Because setting non-empty _name affects behavior of other code.

In most cases __name__ can be derived from __origin__.__name__.
(cherry picked from commit 4ceec495598e78f0776dd46d511dcc612a434dc3)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>