[3.13] gh-143308: fix UAF when PickleBuffer is concurrently mutated in a callback (GH-143312) (#143397)

gh-143308: fix UAF when PickleBuffer is concurrently mutated in a callback (GH-143312)
(cherry picked from commit 6c53af18f61c074d514e677b469b6201573a59da)

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Co-authored-by: Aaron Wieczorek <aaronw@fastmail.com>
Co-authored-by: Aaron Wieczorek <woz@Aarons-MacBook-Pro.local>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>