Fix KubernetesPodOperator dry_run requiring live Kubernetes API client

[Aaryan123456679]

airflow dags test (and calling KubernetesPodOperator.dry_run() directly) failed outside a real cluster because build_pod_request_obj() unconditionally read hook.is_in_cluster to set the airflow_kpo_in_cluster label. That property instantiates a Kubernetes API client, which requires kube credentials/config to be available — something a dry run must not need.

This adds a keyword-only dry_run parameter to build_pod_request_obj() (default False, so existing callers are unaffected) and has dry_run() skip the is_in_cluster lookup when set.

closes: #45812

[Miretpl]

There are couple of unrelated changes in the PR + conflics - could you resolve it?

[Aaryan123456679]

Thanks for flagging this. The branch had two extra commits that were unrelated to this fix (a check_provider_yaml_files.py namespaced-provider crash fix and a Jira provider.yaml conn-field fix) — those were already merged into main separately via #70224 and #70261, which is what caused the conflicts. I dropped both commits and rebased the actual KubernetesPodOperator dry_run fix cleanly onto latest main. The branch now only contains the two files relevant to this PR (pod.py and its test) and is mergeable.

[potiuk]

Thanks — real usability bug. dry_run() existing to show what would be submitted shouldn't require working kube credentials, and self.hook.is_in_cluster instantiates an API client purely to compute a label value. Threading a keyword-only dry_run flag through build_pod_request_obj is the minimal way to fix it, and keyword-only keeps it backward compatible for the many subclasses that override or call this method.

The tests are the right shape: making is_in_cluster raise and asserting the dry-run path survives and the normal path still raises proves the flag actually gates the client instantiation, rather than just that dry_run happens to work.

One consequence worth deciding on inline.

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Drafted-by: Claude Code (Opus 5); reviewed by @potiuk before posting