1. Remove usage of PyEval_ThreadsInitialized and PyEval_InitThreads
Both of these functions were removed in Python 3.13 [1] after being
deprecated since Python 3.9.
According to "What's new in Python 3.13" document [1]:
Since Python 3.7, Py_Initialize() always creates the GIL: calling
PyEval_InitThreads() did nothing and PyEval_ThreadsInitialized()
always returned non-zero.
2. Replace _Py_IsFinalizing() with Py_IsFinalizing().
[1] https://docs.python.org/3.13/whatsnew/3.13.html
b2929bebb6