[core, display, overlay] Add LayerIsOverlay to separate overlay on composer, stub RequestListSummaryOverlayNotification, sync emu settings when setting language (#3123)

This should fix the issue with, for example, ToTK running at 60 FPS when overlay applet is running.
This also should always run the overlay as actual overlay and not in the back.
Stubs RequestListSummaryOverlayNotifications in friends
Syncs Language of the Emulator, when setting language, this is used in Starter Applet

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3123
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Co-authored-by: Maufeat <sahyno1996@gmail.com>
Co-committed-by: Maufeat <sahyno1996@gmail.com>

src/core/hle/service/nvnflinger/display.h

@@ -15,7 +15,7 @@ struct Layer {
     explicit Layer(std::shared_ptr<android::BufferItemConsumer> buffer_item_consumer_,
                    s32 consumer_id_)
         : buffer_item_consumer(std::move(buffer_item_consumer_)), consumer_id(consumer_id_),
-          blending(LayerBlending::None), visible(true), z_index(0) {}
+          blending(LayerBlending::None), visible(true), z_index(0), is_overlay(false) {}
     ~Layer() {
         buffer_item_consumer->Abandon();
     }
@@ -25,6 +25,7 @@ struct Layer {
     LayerBlending blending;
     bool visible;
     s32 z_index;
+    bool is_overlay;
 };
 
 struct LayerStack {