CI: fix image load issue in k3d (#7414)

`k3d` supports [multiple ways of importing images](https://k3d.io/v5.2.0/usage/importing_images/)
in the latest version of k3d. The default way however fails to import
multiple images from the same command. Hence, there is a need to
either
- load one by one using the `direct` mode
- load all at once using the `tools-node` mode.

I've went ahead with the `tools-node` mode, so that we chan
paralellize the image loads.

Signed-off-by: Tarun Pothulapati <tarunpothulapati@outlook.com>

bin/image-load

@@ -149,5 +149,5 @@ fi
 
 if [ -n "$k3d" ]; then
   printf 'Importing %s...\n' "${images[@]}"
-  "$bin" "${image_sub_cmd[@]}" "${images[@]}"
+  "$bin" "${image_sub_cmd[@]}" "${images[@]}" -m tools-node
 fi