[3.13] gh-118851: Default ctx arguments to AST constructors to Load() (GH-118854) (#118871)

(cherry picked from commit 68fbc00dc870f6a8dcbecd2ec19298e21015867f)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>