optimize refcounting op in datetime creation

[davidhewitt]

Change Summary

Followup to #1583.

This changes some try_into_py methods to take self instead of &self, allowing transfer of the Python reference rather than creating a new one.

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 #1590 will not alter performance

_{Comparing dh/into-py-tidy (b9598ba) with main (b5c3e14)}

Summary

✅ 157 untouched benchmarks

[sydney-runkle]

Cool, thanks!