debian.package: Modify boot order

Put our UEFI boot application just before the currently booted element in the list.

debian.package/uefi-boot-metadata-collect-agent/DEBIAN/postinst

@@ -5,6 +5,10 @@ ROOT_DEV=$(mount | grep -Po '^.+(?= on / )')
 
 if ! efibootmgr --disk "$EFI_DEV" --verbose | grep "uefi-boot-metadata-collect-agent.efi"; then
     efibootmgr --create --disk "$EFI_DEV" --label 'UEFI metadata-collect-agent' --loader /uefi-boot-metadata-collect-agent.efi
+    BOOT_CUR=$(efibootmgr | grep -Po '(?<=BootCurrent: ).+')
+    BOOT_AGENT=$(efibootmgr | grep -Po '(?<=Boot)\d+(?=.+UEFI metadata-collect-agent)')
+    NEW_BOOT_ORDER=$(efibootmgr | grep -Po '(?<=BootOrder: ).+' | sed "s/$BOOT_CUR/$BOOT_AGENT,$BOOT_CUR/")
+    efibootmgr -o "$NEW_BOOT_ORDER"
 fi
 
 e2label "$ROOT_DEV" "ROOT" || true