[3.13] gh-117657: Fix TSAN race in QSBR assertion (GH-119887) (#119904)

Due to a limitation in TSAN, all reads from `PyThreadState.state` must be
atomic to avoid reported races.
(cherry picked from commit 90ec19fd33e2452902b9788d4821f1fbf6542304)

Co-authored-by: Sam Gross <colesbury@gmail.com>