HHH-19321: Improve inline documentation for @SuppressWarnings in multiple methods

[plan11plan]

Hello!

This PR enhances inline documentation for methods using @SuppressWarnings("unchecked") to address concerns highlighted in Effective Java: Item 27 – "Eliminate unchecked warnings."

• registerStoredProcedureParameter: Added comments explaining the unchecked conversion from raw Class to a generic type.
• getResultList: Documented the reason behind casting Collections.EMPTY_LIST as List and casting ResultSetOutput to List.
• unwrap: Clarified that runtime type checks (cls.isInstance()) ensure the safety of casting 'this', parameterMetadata, etc.

These changes help maintainers understand why the warnings are suppressed and prevent accidental removal or modification that might compromise type safety.

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https://hibernate.atlassian.net/browse/HHH-19321

[gavinking]

I don't think there's much value to commenting this sort of "obvious" stuff. Much better to actually fix the typing issues and remove the @SuppressWarnings. I did some of that in #9968.