Make FAB AirflowAppBuilder use scoped_session

[trina242]

related: #59349

This PR is yet another attempt to get rid of sqlalchemy.exc.PendingRollbackError in FAB provider caused by duplicated sessions. I believe previously applied fixes #57815 and #58196 were a way to go, although an important change - using scoped_session instead of Session - was overridden later by #58644.

I decided to use scoped_session directly in AirflowAppBuilder as it's safe to use both inside and outside the application due to implicit method access and it simplifies otherwise messy type annotations.

First contribution, please be nice 😉

[boring-cyborg]

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[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.