Add tests for BaseConfigKeys iteration

[lbbc-lh]

Add a dedicated unit test for BaseConfigKeys.__iter__ and remove the matching OVERLOOKED_TESTS entry. This follows the provider test-module coverage work tracked in #35442.

No runtime behavior changes.

related: #35442

Testing

• breeze run pytest providers/amazon/tests/unit/amazon/aws/executors/utils/test_base_config_keys.py airflow-core/tests/unit/always/test_project_structure.py::TestProjectStructure::test_providers_modules_should_have_tests -xvs (2 passed)
• breeze run mypy providers/amazon/tests/unit/amazon/aws/executors/utils/test_base_config_keys.py
• prek run --from-ref upstream/main --stage pre-commit
• breeze testing providers-tests --test-type "Providers[amazon]" (4737 passed, 9 skipped)
• breeze testing core-tests --test-type Always (2020 passed, 66 skipped, 1 xfailed; one unrelated Azure Batch SDK import failure)

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Was generative AI tooling used to co-author this PR?

• Yes — Codex (GPT-5.6 Sol)

Generated-by: Codex (GPT-5.6 Sol) following the guidelines

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Drafted-by: Codex (GPT-5.6 Sol); reviewed by @lbbc-lh before posting

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[Copilot]

Pull request overview

Adds a missing unit test module in the Amazon provider to cover BaseConfigKeys.__iter__, and updates the project-structure “overlooked tests” allowlist accordingly. This supports the ongoing provider test-module coverage effort tracked in #35442 without changing runtime behavior.

Changes:

• Added a dedicated unit test validating BaseConfigKeys iteration returns the subclass’ non-dunder attribute values.
• Removed the corresponding path from OVERLOOKED_TESTS now that the module has a real test file.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
providers/amazon/tests/unit/amazon/aws/executors/utils/test_base_config_keys.py	New unit test covering BaseConfigKeys.__iter__ behavior.
airflow-core/tests/unit/always/test_project_structure.py	Removes the new test file from the OVERLOOKED_TESTS exclusion list.

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[SameerMesiah97]

I know that this PR was opened in response to Issue #35442 but that is almost 3 years old and may not be relevant anymore.

Also, I am struggling to see the value of this new test. It verifies the implementation of BaseConfigKeys.__iter__ using an artificial subclass, but what user-facing or internal contract relies on iteration returning these values?

Maybe you could see if there are genuine gaps that require test coverage in BaseConfigKeys instead of adding a test for its own sake?