[3.14] GH-148726: Forward-port generational GC

[sergey-miryanov]

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📚 Documentation preview 📚: https://cpython-previews--148720.org.readthedocs.build/

• Issue: Forward-port generational GC #148726

[nascheme]

I've done a second pass of review and this looks good to merge. One minor nit, the Include/internal/pycore_interp_structs.h still has the _GCPhase enum, which is now unused.

[nascheme]

@hugovk I believe as release manager, you need to review the ABI changes (should be compatible, IMHO). I think when that's done, we need to commit the updated ABI file into this branch, before we can merge.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @hugovk for commit 39e803e 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F148720%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @hugovk for commit ba7443e 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F148720%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[hugovk]

These buildbots failures look unrelated: pre-existing failures or flaky tests.