See 6b98b274b6 for an explanation of the problem and solution. Here I've applied the solution to channels.
(cherry picked from commit 8b209fd4f8, AKA gh-121805)
Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>
I added it quite a while ago as a strategy for managing interpreter lifetimes relative to the PEP 554 (now 734) implementation. Relatively recently I refactored that implementation to no longer rely on InterpreterID objects. Thus now I'm removing it.
For the most part, these changes make is substantially easier to backport subinterpreter-related code to 3.12, especially the related modules (e.g. _xxsubinterpreters). The main motivation is to support releasing a PyPI package with the 3.13 capabilities compiled for 3.12.
A lot of the changes here involve either hiding details behind macros/functions or splitting up some files.