Fix: Make sqlalchemy optional in Drill provider

[NewSmoke38]

I modified the Drill provider to safely handle the absence of sqlalchemy by wrapping the import in a try-except block. It now raises AirflowOptionalProviderFeatureException in get_conn if the library is missing when actually needed.

Testing:
I verified this manually by running a script that simulates a missing sqlalchemy environment. This confirmed that while the parent DbApiHook typically relies on sqlalchemy, the Drill provider now loads successfully without it and only raises the correct exception when get_conn is called.

I look forward to your feedback.

closes: #59897

[boring-cyborg]

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[sunank200]

We should also mark optional dependency for sqlalchemy in pyproject for drill

[sunank200]

Suggested change

[sunank200]

Suggested change

	raise AirflowOptionalProviderFeatureException("The 'sqlalchemy' library is required to use this hook.")
	raise AirflowOptionalProviderFeatureException(
	"sqlalchemy is required for SQL filter clause generation. "
	"Install it with: pip install 'apache-airflow-providers-drill[sqlalchemy]'"
	)

[jscheffl]

I am actually not sure whether we need this PR and check at-all. Drill-provider has dependency to sqlalchemy-drill>=1.1.0,!=1.1.6,!=1.1.7 defined and this indirectly has the requirement of sqlalchemy. So irrespective of core dependency it is alyways installing sqlalchemy, no conditional check needed in my view.