Clicking backgrd. dimming of editor popup stops input event propagation

A click on the dimmed background of a popup in the editor should stop the input event from propagating to the background.

This solution reuses the system introduced in commit efc3ffb8, taking advantage of the hide() notifications from the modal where we will set the flag "pass_on_modal_close_click(false)" to stop event handling at the viewport input event handling.
The viewport first hides the modal and after marks the input as handled if the flag mentioned above is set.

Fixes #36341

scene/gui/dialogs.cpp

@@ -247,8 +247,10 @@ void WindowDialog::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_POPUP_HIDE: {
-			if (get_tree() && Engine::get_singleton()->is_editor_hint() && EditorNode::get_singleton() && !was_editor_dimmed)
+			if (get_tree() && Engine::get_singleton()->is_editor_hint() && EditorNode::get_singleton() && !was_editor_dimmed) {
 				EditorNode::get_singleton()->dim_editor(false);
+				set_pass_on_modal_close_click(false);
+			}
 		} break;
 #endif
 	}