gh-103202: Proof of concept: OrderedDict.sort()

[Gouvernathor]

See the benchmarks, this is supposed to be the best version performance-wise.
Only sorting the keys is quicker of course, but for that sorted should still be used.

I'm putting this so the tests can execute, but of course this is missing a news entry, a doc entry, a C equivalent, and for the purpose to be accepted - this is a proof-of-concept, mainly, even though I believe it's viable.

• Issue: OrderedDict.sort #103202

[sunmy2019]

Your change won't apply for most cases (you can should add a test case to verify, though). You need to modify Objects/odictobject.c as well.