fix: move getattr warning in deprecated BaseConfig

[tlambert03]

Change Summary

I wonder if you'd consider this small change to the warnings emitted by _ConfigMetaclass.__getattr__.
This warning popped up for me in a situation where pydantic was imported, but not being used, (i.e. I wasn't creating a model with a deprecated config) because another library was calling hasattr() on basically any object it could find (all subclasses of object).

I know that's a bit unusual, but since __getattr__ is called when checking hasattr, I thought it does seem reasonable to let the AttributeError go through in cases of KeyError, and only emit the warning when you're actually getting an attribute.

To give a simple example:

In [1]: import warnings

In [2]: warnings.simplefilter("default")

In [3]: from pydantic.deprecated.config import BaseConfig

In [4]: b = BaseConfig()  # warning makes total sense here
<ipython-input-4-74b49e0b3948>:1: PydanticDeprecatedSince20: BaseConfig is deprecated. Use the `pydantic.ConfigDict` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.2/migration/
  b = BaseConfig()

In [5]: hasattr(b, 'asdfsdf')  # I would expect this to simply return False
/Users/talley/micromamba/envs/ome-types/lib/python3.11/site-packages/pydantic/deprecated/config.py:38: PydanticDeprecatedSince20: Support for class-based `config` is deprecated, use ConfigDict instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.2/migration/
  warnings.warn(_config.DEPRECATION_MESSAGE, DeprecationWarning)
/Users/talley/micromamba/envs/ome-types/lib/python3.11/site-packages/pydantic/deprecated/config.py:21: PydanticDeprecatedSince20: Support for class-based `config` is deprecated, use ConfigDict instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.2/migration/
  warnings.warn(_config.DEPRECATION_MESSAGE, DeprecationWarning)
Out[5]: False

Related issue number

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable
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[tlambert03]

ok, i think it's all set now. Not sure if the relnotes thing is something I can fix or something you have to fix

[alexmojaki]

@Kludex ping

[sydney-runkle]

@tlambert03,

Thanks for the fix. I've fixed the relnotes issue. We'll merge this next week!