Proposal: Officially Deprecate Support for Legacy (Single-Phase Init) Extension Modules

[eric.snow]

@da-woods

I don’t think there’s anything free-threading related that currently requires multi-phase import. You can declare support with Module Objects — Python 3.13.3 documentation.

I have some clarification about PyUnstable_Module_SetGIL(). However, I don’t want discussion of free-threading to take over this thread, which can easily happen. I’ve opened Concerns About PyUnstable_Module_SetGIL() instead.