Code simplifications

CanvasItemEditor:
- p_result == ADD_MOVE is always true in this switch-clause

- both parts of the if-else-clause do the same thing and simplified an affine_inverse call

ControlEditorToolbar:
- private function ControlEditorToolbar::_anchor_to_position is used nowhere. Looks like
copy and paste from CanvasItemEditor::_anchor_to_position

ScrollContainer:
- screen_is_touchscreen is always true, because otherwise the function already returned

TextLine:
- both parts of the if-else-clause do the same thing and simplified return statement

editor/plugins/control_editor_plugin.h

@@ -222,7 +222,6 @@ class ControlEditorToolbar : public HBoxContainer {
 	void _anchor_mode_toggled(bool p_status);
 	void _container_flags_selected(int p_flags, bool p_vertical);
 
-	Vector2 _anchor_to_position(const Control *p_control, Vector2 anchor);
 	Vector2 _position_to_anchor(const Control *p_control, Vector2 position);
 	bool _is_node_locked(const Node *p_node);
 	List<Control *> _get_edited_controls();