Leave it to the new mutator pass IdentifyContainers to replace Class
nodes with Container nodes where appropriate.
This will allow us to run passes over the type graph before identifying
containers, and therefore before we have lost information about the
internal details of the container (e.g. alignment of member variables).
We only want to do the extra work if it's explicitly requested.
chaseRawPointers is already explicitly requested whenever it's needed
and readEnumValues currently isn't needed at all.
