[218] Proper python multithreading

With Python 3.12, we started seeing crashes during certain multithreaded
operations. It turns out that changes to the GIL in 3.12 exposed that we are
not handling Python thread state properly. This commit fixes this.

A new namespace python_state has been added to main.cpp for holding onto some
Python state information, and a new struct python_thread_state_scope has also
been added for managing Python thread state.

This will be improved upon in the future.