[Clang] [Sema] Diagnose unexpanded parameter packs in attributes (#93482)

Call `DiagnoseUnexpandedParameterPack` when we parse an expression
argument to an attribute and check for implicit code in the
`CollectUnexpandedParameterPacksVisitor` so we can actually find
unexpanded packs in attributes that end up applied to lambda call
operators.

This fixes #93269.