validate by iteration

[davidhewitt]

Change Summary

Related to pydantic/jiter#184

By making json object lookup less efficient we should move away from it as much as possible and prefer iteration. We've wanted this anyway for a while as it would be necessary for proper jiter integration.

WIP, I want to introduce a "lookup tree" to handle all the aliases and that madness.

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 #1620 will improve performances by 19.34%

_{Comparing dh/lookup-tree (306c934) with main (741961c)}

Summary

⚡ 1 improvements
✅ 156 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_core_json_fs	134.7 µs	112.9 µs	+19.34%