Fixed sqlalchemy as optional dependency for teradata provider

[sarth-akvaish]

Make sqlalchemy optional dependency for teradata provider

This change makes SQLAlchemy an optional dependency for the Teradata provider. Runtime SQLAlchemy imports are now handled lazily and raise AirflowOptionalProviderFeatureException when the dependency is not installed.

closes : #59907

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[sarth-akvaish]

Hi @potiuk , updated the PR and fixed the static checks which were failing earlier.