BindingDOMWriteTransactionAdapter.ensureParentsByMerge() should skip structural containers

ensureParentsByMerge() emits merge operations for the entire path leading up to the element being introduced.

The DataTree manages lifecycle of non-presence containers, which means these are automatically created as needed, hence an explicit merge is not needed.

Modify the API and implementation to walk the schema context so that a merge is not triggered for non-presence containers.