Data-Driven Tree View Enhancements

[Sarenor]

Describe the feature in detail (code, mocks, or screenshots encouraged)

Events

Currently, a datadriven/recursive TreeView doesn't forward events. To be able to react to changes in the TreeView, it would be nice if the ChangeEvent in the TreeViewDataDrivenItem could bubble through the TreeView until it can be listened to by the caller.

###Ease of use:
Currently, the new datadriven/recursive TreeView marks nodes that have been checked only in the provided TreeViewNodes-List.

For ease of use it would be nice if it could also provide a bind-point for selectedTreeNodes or similar, that contains a list of only the selected nodes.

What type of pull request would this be?

Enhancement

Provide relevant links or additional information.

https://carbon-components-svelte.onrender.com/components/TreeView

The reporting user mentioned Carbon TreeView as a reference, probably mostly for the selectedItems list. Although I only found that for initial selection, but my quick scan probably missed the other part.

Discord Convo

[Tihomir971]

Provide relevant links or additional information.

https://carbon-components-svelte.onrender.com/components/TreeView

The reporting user mentioned Carbon TreeView as a reference, probably mostly for the selectedItems list. Although I only found that for initial selection, but my quick scan probably missed the other part.

Discord Convo

activeId, selectedIds and expandedIds in Carbon TreeView are reactive and can be used both ways

[Mahmoud-zino]

Note: events forwarding is now included in #1910.