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GH-43536: [Python] Do not use borrowed references APIs (#43540)

### Rationale for this change

For better reference safety under Python free-threaded builds (i.e. with the GIL removed), we should be using `Py(List|Dict)_GetItemRef` that return strong references and are implemented in a thread-safe manner.

### What changes are included in this PR?

- Vendor a copy of https://github.com/python/pythoncapi-compat
- Port to strong reference APIs for lists and dicts

### Are these changes tested?

I ran the tests with the free-threaded build before and after, and there's the same expected failures.

* GitHub Issue: #43536

Lead-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>