[3.13] gh-127521: Mark list as "shared" before resizing if necessary (GH-127524) #127533
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In the free threading build, if a non-owning thread resizes a list,
it must use QSBR to free the old list array because there may be a
concurrent access (without a lock) from the owning thread.
To match the pattern in dictobject.c, we just mark the list as "shared"
before resizing if it's from a non-owning thread and not already marked
as shared.
(cherry picked from commit c7dec02)
Co-authored-by: Sam Gross colesbury@gmail.com