[3.12] gh-107576: Ensure `__orig_bases__` are our own in `get_original_bases` (GH-107584) (#107592)

gh-107576: Ensure `__orig_bases__` are our own in `get_original_bases` (GH-107584)
(cherry picked from commit ed4a978449c856372d1a7cd389f91cafe2581c87)

Co-authored-by: James Hilton-Balfe <gobot1234yt@gmail.com>
Co-authored-by: Chris Bouchard <chris@upliftinglemma.net>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>