System: Add an option to preload CD image to RAM

src/core/settings.h

@@ -100,6 +100,7 @@ struct Settings
 
   bool cdrom_read_thread = true;
   bool cdrom_region_check = true;
+  bool cdrom_load_image_to_ram = false;
 
   AudioBackend audio_backend = AudioBackend::Cubeb;
   s32 audio_output_volume = 100;