bpo-44731: Simplify the union type implementation (GH-27318) (GH-27334)

Remove direct support of typing types in the C code because they are already supported by defining methods __or__ and __ror__ in the Python code.

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

Lib/typing.py

@@ -375,6 +375,12 @@ class _SpecialForm(_Final, _root=True):
     def __call__(self, *args, **kwds):
         raise TypeError(f"Cannot instantiate {self!r}")
 
+    def __or__(self, other):
+        return Union[self, other]
+
+    def __ror__(self, other):
+        return Union[other, self]
+
     def __instancecheck__(self, obj):
         raise TypeError(f"{self} cannot be used with isinstance()")