value: Always add the type name to elements when serializing arrays/lists

value: Always add the type name to elements when serializing arrays/lists

But only when serializing outside of GstStructures, because in case of
GstStructure the type is already preprended to the array/list and the
GstStructure API makes sure that they have the same "generic" type so
deserialization works properly.

This keeps serialization of GstStructures the same as before, and the
GstCaps unit tests already test for that. However when serializing
standalone arrays/lists get the types added now.