Kind cluster snapshot and restore

[bjorn-amd]

Description

This snapshots a kind cluster by compressing everything from the /var directory into /var_snapshot.tar.gz and saving the container as a new image. Restore works in reverse, that it remaps a snapshotted container to the kind cluster, extracts /var_snapshot.tar.gz into /var and restarts the cluster.

time bash ./test/scripts/setup_kind.sh --skip-static 
...
Cluster is ready!
bash ./test/scripts/setup_kind.sh --skip-static  65.64s user 40.88s system 22% cpu 7:48.99 total

time sh -c "kind create cluster --name kaiwo-test --config ../kind/kind-test-cluster.yaml && ./restore_kind.sh 0.1"
...
Restore complete!
sh -c   2.89s user 6.39s system 8% cpu 1:53.02 total

(note that the restore doesn't do any network traffic in this example, it will take longer when images need to be downloaded)

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project. See contributing-guidelines.md
• Existing workload examples run to completion after my changes (if applicable)
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[AVSuni]

Thanks for this. Looks great! Some ideas for improving:

• Let's create a GHA job for making the snapshot. This should only run when something changes under dependencies directory and is pushed to main. The built images should be pushed to registry. snapshot_kind.sh should only ever be run in CI.
• restore_kind.sh should pull from registry
• restore_kind.sh should work the same in CI and locally