Fix missing wl_surface.enter events for outputs enabled at runtime. (…

…#3585)

In my [previous fix](#3430) for
#3414, I accidentally disabled sending `wl_surface.enter` events for
surfaces on outputs enabled at runtime. This PR resolves that issue
while still addressing #3414.

src/server/frontend_wayland/output_manager.cpp

@@ -224,7 +224,10 @@ void mf::OutputGlobal::bind(wl_resource* resource)
 {
     auto const instance = new OutputInstance(resource, this);
     instances[instance->client].push_back(instance);
-    instance->output_config_changed(output_config);
+    for (auto const& listener : listeners)
+    {
+        listener->output_config_changed(output_config);
+    }
     instance->send_done();
 }