* Expose the focused element and event in the TreeView API
* Exposed active TreeItem through extension proposal
* Add proposal to test extension
* Merge change selection and focus events
* Finish selection+focus change in treeview
* Clean up
* Clean up
* Add checkProposedApiEnabled back in
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Co-authored-by: Ehab Younes <ehab.younes@sigasi.com>
Co-authored-by: Alex Ross <alros@microsoft.com>