Signature for the SemanticsConfiguration.childConfigurationsDelegate.
The input list contains all SemanticsConfigurations that rendering children want to merge upward. One can tag a render child with a SemanticsTag and look up its SemanticsConfigurations through SemanticsConfiguration.tagsChildrenWith.
The return value is the arrangement of these configs, including which configs continue to merge upward and which configs form sibling merge group.
Use ChildSemanticsConfigurationsResultBuilder to generate the return value.
typedef ChildSemanticsConfigurationsDelegate = ChildSemanticsConfigurationsResult Function(List<SemanticsConfiguration>);