resolve remaining deprecation warnings from PyO3 0.23

[davidhewitt]

Change Summary

This primarily removes uses of the ToPyObject trait in favour of IntoPyObject. The hardest bit was in the Input trait, which had previously used ToPyObject as a super-trait. Instead I now added a defaulted .to_object method on Input to minimise changes.

Related issue number

N/A

Checklist

• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• Pydantic tests pass with this pydantic-core (except for expected changes)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codspeed-hq]

CodSpeed Performance Report

Merging #1584 will improve performances by 10.25%

_{Comparing dh/final-0.23-fixups (36d414a) with main (d3a2f47)}

Summary

⚡ 1 improvements
✅ 156 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	dh/final-0.23-fixups	Change
⚡	test_frozenset_of_ints_duplicates_core	170.9 µs	155 µs	+10.25%

[davidhewitt]

Will investigate the enum perf regressions before this is ready for merge.

[davidhewitt]

Gonna ship 🚀