gh-135034: Normalize link targets in tarfile, add `os.path.realpath(strict='allow_missing')` (#135037)

Addresses CVEs 2024-12718, 2025-4138, 2025-4330, and 2025-4517.

Signed-off-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Seth Michael Larson <seth@python.org>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>