Reuse basic validators and serializers

[davidhewitt]

Change Summary

This diff wraps all validators and serializers across the codebase in Arc, for two reasons:

• This makes it possible to re-use simple validators, making progress to reduce memory usage observed in Memory Usage From Schema Validators Is Fairly High, Even With Simple Models pydantic#12272
• It makes it possible to do further optimizations:
  • Re-use of portions of serializer / validator trees (left for future follow up, figuring out where to deduplicate is hard)
  • Tree traversal algorithms which rewrite portions of trees (this would allow schema cleaning to move into Rust)

In this PR, the memory usage from the repro in #12272 falls from about 600KB per model to 500 KB. We should be able to do more to improve this based on the follow ups.

Related issue number

Partial improvement for pydantic/pydantic#12272

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 #1795 will not alter performance

_{Comparing dh/arc-validators (d9dbeeb) with main (ecbc893)}

Summary

✅ 163 untouched

[Viicos]

Nice! Seems like caching simple validators is straightforward, going to be more challenging for more complex cases.