GenericSubsystemDescribeHandler generates duplicates operations for override models

Currently, GenericSubsystemDescribeHandler relies on ImmutableManagementResourceRegistration.getChildAddresses(...) to find child resources. When processing a wildcard address, all resource children are matched. Thus any non-wildcard paths returned by getChildAddresses(...) for the same child type will end up being described twice. Additionally, child order needs to be preserved, even in the presence of override models.