[3.12] gh-53203: Fix test_strptime on Solaris (GH-125785) (GH-125807)

Use fixed timezone.
Skip roundtrip tests on locales with 2-digit year.
(cherry picked from commit 9dde4638e44639d45bd7d72e70a8d410995a585a)

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