Add support for extra keys validation for model fields

[Viicos]

Change Summary

Part of pydantic/pydantic#9400.

This is only implemented for model fields but this could be done for dataclass/typed dict as well. I only went with models for now as it is the only data type where extra validation can be customized through __pydantic_extra__.

This also only implements validation support. Extra values can have serialization customized but I don't think we should also allow serialization customization for extra keys as we don't have such a concept for "normal" field names.

Related issue number

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 #1671 will not alter performance

_{Comparing extra-keys-validation (651657c) with main (ac17f0c)}

Summary

✅ 157 untouched benchmarks