gh-90494: Reject 6th element of the __reduce__() tuple (GH-93609) (GH-93631)

copy.copy() and copy.deepcopy() now always raise a TypeError if
__reduce__() returns a tuple with length 6 instead of silently ignore
the 6th item or produce incorrect result.
(cherry picked from commit a365dd64c2)

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

Lib/copy.py

@@ -258,7 +258,7 @@ def _keep_alive(x, memo):
 
 def _reconstruct(x, memo, func, args,
                  state=None, listiter=None, dictiter=None,
-                 deepcopy=deepcopy):
+                 *, deepcopy=deepcopy):
     deep = memo is not None
     if deep and args:
         args = (deepcopy(arg, memo) for arg in args)