Fix lint errors with toolchain 1.83

[changhc]

Change Summary

Fixes lint errors that came up with the new stable toolchain version 1.83. Simply followed the tools' suggestions. Specifically for clippy::used_underscore_items though,

• for _invalid_as_json_key, I removed the prefix underscore because that was rather simple and there was no conflict in naming.
• for others, I applied #[allow(clippy::used_underscore_items)] to suppress the warning because there would be a collision and I cannot really decide on naming. Perhaps someone can revisit that later on.

Same for clippy::type_complexity in src/serializers/shared.rs.

Related issue number

Fixes #1560.

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

[codecov]

Codecov Report

Attention: Patch coverage is 57.69231% with 11 lines in your changes missing coverage. Please review.

Project coverage is 89.63%. Comparing base (ab503cb) to head (c253d6d).
Report is 241 commits behind head on main.

Files with missing lines	Patch %	Lines
src/validators/with_default.rs	40.00%	3 Missing ⚠️
src/serializers/fields.rs	0.00%	1 Missing ⚠️
src/serializers/shared.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/complex.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/dict.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/generator.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/list.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/set_frozenset.rs	0.00%	1 Missing ⚠️
src/serializers/type_serializers/union.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1561      +/-   ##
==========================================
- Coverage   90.21%   89.63%   -0.59%     
==========================================
  Files         106      112       +6     
  Lines       16339    17889    +1550     
  Branches       36       40       +4     
==========================================
+ Hits        14740    16034    +1294     
- Misses       1592     1835     +243     
- Partials        7       20      +13     

Files with missing lines	Coverage Δ
src/errors/validation_exception.rs	93.27% <ø> (+0.39%)	⬆️
src/input/datetime.rs	94.69% <ø> (-4.08%)	⬇️
src/input/input_abstract.rs	39.53% <ø> (-30.71%)	⬇️
src/input/input_json.rs	91.36% <ø> (+2.43%)	⬆️
src/input/input_python.rs	98.05% <ø> (+0.84%)	⬆️
src/input/input_string.rs	52.68% <ø> (+14.45%)	⬆️
src/input/return_enums.rs	86.18% <ø> (+0.46%)	⬆️
src/serializers/computed_fields.rs	97.84% <ø> (+0.16%)	⬆️
src/serializers/infer.rs	94.15% <ø> (-0.97%)	⬇️
src/serializers/ser.rs	25.27% <ø> (+0.27%)	⬆️
... and 13 more

... and 41 files with indirect coverage changes

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[codspeed-hq]

CodSpeed Performance Report

Merging #1561 will not alter performance

_{Comparing changhc:lint-1.83 (c253d6d) with main (5c96bec)}

Summary

✅ 155 untouched benchmarks

[davidhewitt]

Thanks, all LGTM 👍