Add rollout upgrade integration test

[bschimke95]

Summary

Adds a test that creates a HA workload cluster and upgrades it from 1.29 Kubernetes to 1.30.

Implementation details

• Non-HA clusters require in-place updates which are currently not supported
• We don't have snapd on the docker infra and cannot install different versions via snap install. That's why we build two different docker images and replace the infrastructure reference accordingly along with the upgrade. On other infra providers we would simply change the version and not the image.
• Right now, we inject a Kubernetes override into the docker build process as we don't have another minor release besides 1.30. Once 1.31 is out, we can bump the test versions, upgrade from 1.30 -> 1.31 and remove this hack in the build process.

Notes

This tests require canonical/microcluster#197 to land in microcluster and canonical/k8s-snap#560 and canonical/k8s-snap#562 to land in k8s-snap.

[addyess]

Just comments. I don't feel like I can give better feedback

[neoaggelos]

Overall LGTM, left some comments around structure

[HomayoonAlimohammadi]

LGTM, Thanks a lot @bschimke95! Just some minor comments and questions.

[bschimke95]

The upgrade test passes, the other tests are known to be faulty/flaky and will be fixed as follow-up work.