Update check_test_naming.py
Changes made:

1. Removed unnecessary import of `annotations` from `__future__`.
2. Simplified the `find_names` function to handle both `ast.Name` and `ast.Attribute`.
3. Combined the `_is_fixture` and `_is_register_dtype` functions into `is_fixture` and `is_register_dtype`.
4. Replaced `any()` with a generator expression to check for conditions in a more concise way.
5. Changed function and variable names to follow snake_case naming convention.
6. Made the code more readable and removed redundant code.

- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

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