Clarify how the name of the prefetch key should be used in the context of evaluating a CQL library (if it should be used at all).

For example, the description for prefetchData.key states:

This typically corresponds to the name of a parameter in a library, or the name of a prefetch item in a CDS Hooks discovery response

If the prefetch key does match a parameter name, should it be supplied as a parameter value to the library? If it does not match a parameter name, does the prefetch key have any additional meaning?

This clarification is important to ensure consistent behavior across implementations.