Use weston_compositor_add_destroy_listener_once() in plugins

This introduces a new convention of checking through the compositor destroy
listener if the plugin is already initialized. If the plugin is already
initialized, then the plugin entry function succeeds as a no-op. This makes it
safe to load the same plugin multiple times in a running compositor.

Currently module loading functions return failure if a plugin is already
loaded, but that will change in the future. Therefore we need this other method
of ensuring we do not double-initialize a plugin which would lead to list
corruptions the very least.

All plugins are converted to use the new helper, except:
- those that do not have a destroy listener already, and
- hmi-controller which does the same open-coded as the common code pattern
  did not fit there.

Plugins should always have a compositor destroy listener registered since they
very least allocate a struct to hold their data. Hence omissions are
highlighted in code.

Backends do not need this because weston_compositor_load_backend() already
protects against double-init. GL-renderer does not export a standard module
init function so cannot be initialized the usual way and therefore is not
vulnerable to double-init.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

pipewire/pipewire-plugin.c

@@ -797,6 +797,13 @@ weston_module_init(struct weston_compositor *compositor)
 	if (!pipewire)
 		return -1;
 
+	if (!weston_compositor_add_destroy_listener_once(compositor,
+							 &pipewire->destroy_listener,
+							 weston_pipewire_destroy)) {
+		free(pipewire);
+		return 0;
+	}
+
 	pipewire->virtual_output_api = api;
 	pipewire->compositor = compositor;
 	wl_list_init(&pipewire->output_list);
@@ -821,11 +828,10 @@ weston_module_init(struct weston_compositor *compositor)
 			"Debug messages from pipewire plugin\n",
 			NULL, NULL, NULL);
 
-	pipewire->destroy_listener.notify = weston_pipewire_destroy;
-	wl_signal_add(&compositor->destroy_signal, &pipewire->destroy_listener);
 	return 0;
 
 failed:
+	wl_list_remove(&pipewire->destroy_listener.link);
 	free(pipewire);
 	return -1;
 }