Various reference leaks in the core

[JelleZijlstra]

Bug report

Bug description:

I found a handful of reference leaks in the core using Codex. PR incoming.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-145376: Fix various reference leaks #145377
• gh-145376: Fix various reference leaks objects and modules #145385
• gh-145376: Fix reference leaks in _collectionsmodule.c #145421
• gh-145376: Fix null pointer deref in md5module.c #145422
• gh-145376: Avoid reference leaks in failure path of _functoolsmodule.c method partial_new #145423