Retain grouping/uses instantiation vectors

binding-dom-codec requires information about grouping instantiation within an instance of BindingRuntimeTypes to make leafref mapping predictable.

If can have the equivalent of

populated for each encountered grouping, we can find the corresponding leafref resolution information available via the footprint left by AbstractTypeObjectGenerator.addAsGetterMethodOverride() in GeneratedType. Backreferences stored here should point to instantiation roots, i.e. where a uses statement causes a grouping (and all its referenced grouping) to be referenced when the corresponding SchemaInferenceStack.isGrouping() == false. The footprint can be examined by inquiring GeneratedType.getImplements() type hierarchy.