Add backward compatibility for core__sql_alchemy_conn__cmd

[c-thiel]

This adds backwards compatibility to use the __cmd option on core__sql_alchemy_conn which was lost in the 2.3.0 update.

closes: [#23408]
related: [#23408]

[boring-cyborg]

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[potiuk]

Small static check probiem :)

[potiuk]

Thanks for submitting that BTW!

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!