Re-work picking dialog into 3 panel view
Picking panel is redesigned to use 3 panel view: parent project/collection, center project/collection, and details of currently selected item.
Should support browsing and picking files, directories and projects. Must support selecting a single item or multiple items.
The is the two-panel browsing design from #18645 with the addition of a 3rd panel showing details.
For this story, we are putting aside search for the time being. Will follow up in #18775