fix(iso): restore memtest menu entries and validate ISO

iso/builder/config/bootloaders/grub-pc/grub.cfg

@@ -29,6 +29,16 @@ menuentry "EASY-BEE (fail-safe)" {
     initrd  @INITRD_LIVE@
 }
 
+if [ "${grub_platform}" = "efi" ]; then
+    menuentry "Memory Test (memtest86+)" {
+        chainloader /boot/memtest86+x64.efi
+    }
+else
+    menuentry "Memory Test (memtest86+)" {
+        linux16 /boot/memtest86+x64.bin
+    }
+fi
+
 if [ "${grub_platform}" = "efi" ]; then
     menuentry "UEFI Firmware Settings" {
         fwsetup

iso/builder/config/bootloaders/isolinux/live.cfg.in

@@ -22,3 +22,7 @@ label live-@FLAVOUR@-failsafe
     linux @LINUX@
     initrd @INITRD@
     append @APPEND_LIVE@ bee.nvidia.mode=gsp-off memtest noapic noapm nodma nomce nolapic nosmp vga=normal
+
+label memtest
+    menu label ^Memory Test (memtest86+)
+    linux /boot/memtest86+x64.bin