[3.12] gh-107080: Fix Py_TRACE_REFS Crashes Under Isolated Subinterpreters (gh-107567) (#107599)

gh-107080: Fix Py_TRACE_REFS Crashes Under Isolated Subinterpreters (gh-107567)

The linked list of objects was a global variable, which broke isolation between interpreters, causing crashes. To solve this, we've moved the linked list to each interpreter.
(cherry picked from commit 58ef74186795c56e3ec86e8c8f351a1d7826638a)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>