Remove sqlite provider from preinstalled and use aiosqlite as core dep

[potiuk]

Aiosqlite has never been used by the sqlite provider it is really needed as async extension in case Airflow would be configured with async engine. So if we are removing sqlite provider as preinstalled, we should move aiosqlite as required depdendency of core as otherwise creating async sqlite engine will fail.

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[ashb]

Sounds good to me -- aiosqlite is a tiny pure-python dep too

[potiuk]

OK. I had to also importorskip the test_connection tests based on presence of the SQLite Provider - because that's what lower-dep test does now - it removes the sqlite provider because it is not required dependency.

[potiuk]

That's probably not the best way of handling it - idealy we should move those failing tests to provider, but I think it's good for now.

[potiuk]

Merging it. There is a new problem exposed by failing docker build test but this one is related to old setuptools version and new wheel - I will solve it separately.