CORE-3003 Updated DataNavigationPanel drag-n-drop.

Updated the TreePanelDropTargetImpl inside DataNavigationPanel to override less methods, which handle updating the style highlighting of drop-target folders in the tree.
CORE-3744 DataNavigationPanel lazy-loading fixes.

This commit partially reverts 427df9a56069282582338e9736130471a57f942a and bb6714137d82fe49f09ddba4c824f232aea62878.
The lazy-load callback was lingering when lazy-loading wasn't required, causing the callback to attempt to select null folders or select a folder that was previously lazy-loaded even when the user only expands a folder in the navigation folder without selecting anything.