Split Apple platform target and move platform state ownership

src/platform_windows/windows_platform_services.cpp

@@ -793,4 +793,9 @@ PlatformServices& platform_services()
     return services;
 }
 
+VrSessionSnapshot read_platform_vr_session_snapshot() noexcept
+{
+    return read_vr_session_snapshot(retained_state().vr);
+}
+
 }