[Tree] Improve navigation with row select mode

[AThousandShips]

Allows navigating with the ui_left/right actions when selecting rows, fixing a navigation inconsistency

Now pressing ui_left on an expanded item with children collapses it, just like with other selection modes, and moves up otherwise (specialized behavior due to column count), and pressing ui_right expands a collapsed item, and moves down otherwise (again specialized behavior)

To test this open help search and navigate there

Discovered while working on:

• EditorHelpSearch improvements  #62524

[akien-mga]

Thanks!

[AThousandShips]

Thank you!