gh-113308: Restore uuid._load_system_functions for 3.13

[gpshead]

The do nothing private uuid._load_system_functions() function has been restored to appease a PyPI library that calls it to unblock 3.13 testing by others. It now triggers a :exc:DeprecationWarning instead.

This should deal with users blocked by the library on PyPI using the no-op from testing on 3.13:
spulec/freezegun#534 (comment)

• Issue: uuid has a bunch of deprecated functions: let's decide what to do with them #113308

[gpshead]

The PR that removed it was #115934.

[aeros]

I did a search across all repositories using _load_system_functions() and it seems like it is wise to keep it around for some time. https://github.com/search?q=%22_load_system_functions%28%29%22&type=code&p=2

[hugovk]

Those search results look like they're in forks of CPython or the freezegun library, so it doesn't look like it's actually used much (see also my search in gh-113308).

I'm absolutely fine with merging this, but am I right that it's not needed if freezegun makes a new release?

If so, may I suggest waiting until a bit closer to the next 3.13 release (beta 1, 2024-05-07), to give them a chance to make a release?

[gpshead]

am I right that it's not needed if freezegun makes a new release?

Quite possibly. I'm just doing it to be conservative so that even if that doesn't happen we'll unblock things from our end on this issue.

[bblommers]

FYI @hugovk @gpshead : freezegun just had a release where the call to uuid._load_system_functions() is gated, so this seems indeed no longer necessary

[gpshead]

sweet, thanks!