Add pre-commit hook to prevent test-only imports in production source

[shahar1]

related: #60662

Adds a pre-commit hook that prevents test-only module imports from leaking into production source code (*/src/). This addresses the class of bugs demonstrated by #61673, where a tests_common import in the kubernetes provider caused a ModuleNotFoundError at runtime.

The hook detects two categories of forbidden imports:

1. tests_common.* — the apache-airflow-devel-common package is dev-only.
2. *.tests.* / tests.* — any import whose module path contains a .tests. component (e.g. from providers.cncf.kubernetes.tests.foo import bar). Test directories are not shipped in package wheels.

Note (S.E.): the latter should be a relatively low risk because of how the current namespaces work. It could be somewhat helpful in case you messed up the imports while working locally, but such cases could be indicated quickly. I could remove if it's an overkill, the tests_common use case is more prone.

Strictness (see comment on the PR regarding necessity):
All imports from these modules are forbidden, including those guarded by if TYPE_CHECKING:.

This PR also fixes an existing violation in BashOperator (standard provider) by moving ArgNotSet compatibility logic to version_compat.py.

The hook is AST-based (similar to check_airflow_imports_in_shared.py) and runs on all src/ files.

---

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

• Yes (GitHub Copilot)

Generated-by: GitHub Copilot following the guidelines

[jason810496]

It seems we haven't added corresponding entry in .pre-commit-config.yaml.

[shahar1]

It seems we haven't added corresponding entry in .pre-commit-config.yaml.

Yeah, just figured that I've missed it :)
Also, I'm expanding it to imports from tests in general (not only test_common).

[github-actions]

Backport failed to create: v3-1-test. View the failure log Run details

Status	Branch	Result
❌	v3-1-test

You can attempt to backport this manually by running:

cherry_picker 6983599 v3-1-test

This should apply the commit to the v3-1-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

If you don't have cherry-picker installed, see the installation guide.

[jscheffl]

Cool!