Airgapped installation of containers

[vasilvas99]

We need to be able to install containers in a no-internet environment. The current PR sets-up a mechanism to do so.

Concept

1) Define a new distro-feature and a BitBake variable pointing to the location of the pre-downloaded images in the final distro:

    DISTRO_FEATURES += " airgap-containers"
    PREINSTALLED_CTR_IMAGES_DIR = "/data/var/containers/images"

2) Define a new packagegroup packagegroup-sdv-airgap-containers that includes all the recipes based on the sdv-container-cache bbclass which download and copy the container the tar-files to ${D}/data/var/containers/images. This packagegroup is only included in the sdv-image-data image if the new distro feature is enabled

3) Create a script and systemd oneshot service that get installed as part of the "core package group" only if the distro feature is enabled:

• The airgap-container-installer script goes through the directory containing the pre-downloaded tar files and invokes ctr image load to load the image into containerd's registry.
• Since the import is slow (even for images that have already been imported), after ctr image import the name of the tar file is logged in a "lock" file.
• Images logged in the lock are skipped on subsequent runs of the script (improves subsequent boot times 20 s vs < 1s)

Other

• The bitbake recipes for downloading the tar archives have been updated to reflect the images described in the kanto-manifests
• Otel exported/agent have been skipped for now, since their manifests are not ready yet

[vasilvas99]

For discussion: Should the installer script be moved to leda-utils?