Cleanup API symbols

Services expose same sdk_headers as OFW
Since settings apps use some of those symbols, need to include them
Workaround is mock imports by #include the .c code
Not ideal, but we only need access to basic load/save functions, and these apps are bundled with firmware anyway, so should be fine
Not exposing via API and instead bundling via FAP also means less flash used, and RAM is not a concern with settings apps

applications/services/notification/application.fam

@@ -8,5 +8,5 @@ App(
     provides=["notification_settings"],
     stack_size=int(1.5 * 1024),
     order=100,
-    sdk_headers=["notification.h", "notification_messages.h", "notification_app.h"],
+    sdk_headers=["notification.h", "notification_messages.h"],
 )