fix interaction between extra != 'ignore' and from_attributes=True

[davidhewitt]

Change Summary

This is a bugfix to set the interaction between extra and from_attributes to match the pre-2.7 behaviour.

To be honest, I don't love it, basically if from_attributes is set then extra basically always functions as "ignore". I can sort of see why, and we didn't intend to change it in 2.7, but I wonder if there's more satisfying long-term behaviour.

Related issue number

Fixes pydantic/pydantic#9242
Fixes pydantic/pydantic#9250

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

Selected Reviewer: @samuelcolvin

[davidhewitt]

please review

[codspeed-hq]

CodSpeed Performance Report

Merging #1275 will degrade performances by 14.14%

_{Comparing dh/extra-from-attributes (c150587) with main (91c3541)}

Summary

❌ 1 (👁 1) regressions
✅ 154 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	dh/extra-from-attributes	Change
👁	test_strict_union_error_core	53.7 µs	62.6 µs	-14.14%

[sydney-runkle]

Looks great, thanks for looking into this!