pass SerializationState around

[davidhewitt]

Change Summary

This PR changes the serialization code paths to pass &mut SerializationState around, similar to the validation code path.

At the moment this is a large-ish +ve diff. I will follow it up with changes to move include / exclude / extra into the state, which will reduce code size and complexity overall.

Please forgive me, I'm going to just proceed to merge this so I can move forward with the refactoring. The changes here are all mechanical internal refactoring.

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 #1857 will improve performances by 13.25%

_{Comparing dh/ser-state-warnings (3a29497) with main (eed392b)}

Summary

⚡ 2 improvements
✅ 161 untouched

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_json_any_list_int	228.7 µs	207.8 µs	+10.05%
⚡	test_to_json_list_of_lists	2.1 ms	1.8 ms	+13.25%