Emit signals for GraphEdit multi-node selection and unselection
Emit signals for GraphEdit multi-node selection and unselection

Emit `node_selected` and `node_deselected` signals where appropriate
when selecting or unselecting multiple GraphEdit nodes at once.

(cherry picked from commit c1d5c7727cc9a537ec81f007be0b0987ccac91df)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot