getSubContainerDataUpdates

Updates the panel sub-container data associated to the existing panel sub-container view models.

If the returned collection doesn't contain an entry for the panel sub-container, its removal is initiated.

Called whenever panelContainerViewModel is changed. PanelSubContainerViewModels can trigger a panelContainerViewModel change by changing a property that uses the PanelSubContainerViewModel.mutableExtraState delegate.