Add SQLAlchemy dependency to Exasol provider (#59902)

[Jkhall81]

Add SQLAlchemy dependency to Exasol provider

closes: #59902

Summary

This PR makes sqlalchemy an optional dependency for the Exasol provider to support the upcoming Task SDK isolation in Airflow 3.0.

[boring-cyborg]

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[sunank200]

We should mark SQLAlchemy as optional dependency in Exasol pyproject as well

[boring-cyborg]

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