[3.13] gh-60462: Fix locale.strxfrm() on Solaris (GH-138242) (GH-138449)

It should interpret the result of wcsxfrm() as a sequence of abstract
integers, not a sequence of Unicode code points or using other encoding
scheme that does not preserve ordering.
(cherry picked from commit 482fd0c811a366f25bd076fc73bf37ffb6b3081e)

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