[3.13] gh-143547: Fix PyErr_FormatUnraisable() fallback (GH-143557) (GH-143603) (#143612)

[3.14] gh-143547: Fix PyErr_FormatUnraisable() fallback (GH-143557) (GH-143603)

gh-143547: Fix PyErr_FormatUnraisable() fallback (GH-143557)

Hold a strong reference to 'hook' while calling the default
unraisable took to log hook failure.
(cherry picked from commit 1d0baf1ae48f98b61cc869a82e1b7206298f653f)


(cherry picked from commit 39a2bcf949095bd603f7b73f15b5b478dbb49ba9)

Co-authored-by: Victor Stinner <vstinner@python.org>