xdg-activation: distinguish activation and urgency requests

Check if the app that requested a token has provided a valid input
serial and a focused surface. Downgrade activation request to urgency
otherwise.

This is mostly in line with what other Wayland compositors decided to
do, and offers a better security than the original logic.

(cherry picked from commit d19810eba8)

include/sway/desktop/launcher.h

@@ -14,6 +14,7 @@ struct launcher_ctx {
 	struct wl_listener seat_destroy;
 
 	bool activated;
+	bool had_focused_surface;
 
 	struct sway_node *node;
 	struct wl_listener node_destroy;

include/sway/tree/view.h

@@ -277,6 +277,11 @@ void view_set_activated(struct sway_view *view, bool activated);
  */
 void view_request_activate(struct sway_view *view, struct sway_seat *seat);
 
+/*
+ * Called when the view requests urgent state
+ */
+void view_request_urgent(struct sway_view *view);
+
 /**
  * If possible, instructs the client to change their decoration mode.
  */