gh-76785: Improved Subinterpreters Compatibility with 3.12 (1/2) (gh-126704)

These changes makes it easier to backport the _interpreters, _interpqueues, and _interpchannels modules to Python 3.12.

This involves the following:

* rename several structs and typedefs
* add several typedefs
* stop using the PyThreadState.state field directly in parking_lot.c