This commit :
1. Replace CILIUM_RUNTIME_IMAGE variable set in cilium images (cf. Dockerfiles) with the cilium-runtime image variable set in set-env-var action.
2. Changes the sed commands present in images/runtime/update-cilium-runtime-images.sh :
    - Changing the way the image variable is set inside the script. Before that the image was a constant, now it will be extracted from the image_full variable passed as parameter of the script.
    - For Dockerfile, it will not check what is prefixed and will update the image based on its name, so if any changes are name for any reason on prefixed image name on Dockerfiles this won't disrupt the image tag/digest update.
        example :
            if CILIUM_RUNTIME_IMAGE=quay.io/cilium/cilium-runtime:tag@digest
            is changed for RUNTIME_IMAGE=quay.io/cilium/cilium-runtime:tag@digest (or any other name)
            this won't affect the update process
    - For workflows, since the runtime image has been moved to an action (set-env-var), we now look on the .github/actions directory.
      Also added a double quote character to be sure no templating issue will be encountered when updating the set-env action.
3. Changes images/scripts/update-cilium-runtime-images.sh, used to lint cilium runtime images in CI, by removing the image name from a constant variable to a parameter passed along the call of the script.
   We are keeping quay.io/cilium/cilium-runtime as default parameter in the makefile, if nothing is provided to the script/target. But we allow ourselves the possibility to override this variable.

This will allow us to change the repository of the runtime image without having to change the whole image build/lint process.

Signed-off-by: Antony Reynaud <antony.reynaud@isovalent.com>

Signed-off-by: André Martins <andre@cilium.io>