Specifying the same treebuilder config but different code in the `.toml` causes unexpected behaviour

[JakeHillion]

The container .toml should carry all but the treebuilder logic for a type. However, due to implementation details, there is currently only one code provided per enum that treebuilder expects. This means that although the container .toml can have different code bodies but the same treebuilder, only one of the codes is used. Fix this by carrying the ContainerInfo around, perhaps in a shared pointer, rather than using the string map.