Updates Concord APIs in Roslyn to add new field "CustomTypeInfo" which is passed between an managed expression complier and a result provider.
This new field is a new value type "DkmClrCustomTypeInfo", which is used to convey complier specific type information that is not represented by .NET data types (such as C#'s 'dynamic' type).
In Roslyn, this commit also updates the ResultProvider's mock implementation of the Concord API and fixes all affected callsites.