[AIP-94] Route airflow providers get through the API server

[yuseok89]

relates: #68402

WIP — depends on providers list merging first. I'll rebase on top of it, then continue with the remaining providers commands.

Routes airflow providers get through the API server and deprecates it for the new airflowctl providers get (no single-provider endpoint, so it filters GET /providers by package name).

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  • Opus 4.8

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