[3.9] gh-99612: Fix PyUnicode_DecodeUTF8Stateful() for ASCII-only data (GH-99613...

[3.9] gh-99612: Fix PyUnicode_DecodeUTF8Stateful() for ASCII-only data (GH-99613) (GH-107224) (#107231)

Previously *consumed was not set in this case.
(cherry picked from commit f08e52ccb027f6f703302b8c1a82db9fd3934270).
(cherry picked from commit b8b3e6afc0a48c3cbb7c36d2f73e332edcd6058c)

Origin: upstream, https://github.com/python/cpython/commit/4a793281956db0e4a1ca5fdc5f3a0e91f331a75d

Gbp-Pq: Name CVE-2025-4516-5.patch