[clang] Don't short-circuit constant evaluation for array or record types

FastEvaluateAsRValue returns `true` without setting a result value for when a
given constant expression is an array or record type.

Clang attributes must be able to support constant expressions that are array or
record types, so proceed with the slower path for evaluation in the case where
`FastEvaluateAsRValue` does not yield an evaluation result.

Differential Revision: https://reviews.llvm.org/D141745