Implement upgrade of the cluster

[kdomanski]

This issue tracks progress on implementing cluster upgrades with KubeOne.

Acceptance criteria:

• Operator can upgrade KubeOne cluster using command such kubeone upgrade (Implement core scripts and logic for running upgrades #211)
• kubeone upgrade takes care of upgrading workers (MachineDeployments) (Upgrade MachineDeployments #214)
• kubeone upgrade takes care of upgrading components we deploy on the cluster, such as machine-controller and Ark (kubeone upgrade takes care of upgrading machine-controller #236)
• We're testing do upgrades work correctly as part of our E2E tests

Planning:

• Write a proposal for handling cluster upgrades ([proposal 0002] kubeone upgrade #190)

Implementation:

• Create kubeone upgrade CLI command (Build new kubeone upgrade CLI command #196, upgrade CLI #201)
• Implement preflight checks (Upgrades: Implement preflight checks #206)
• Implement core scripts and logic for running upgrades (package upgrades and kubeadm upgrade) (Implement core scripts and logic for running upgrades #211)
• Upgrade MachineDeployments after upgrading control plane nodes (Upgrade MachineDeployments #214)

Consider:

• Backup critical components before running upgrade process
• Build add-on manager for managing and updating components we deploy on cluster, such as machine-controller and Ark

[xmudrii]

/unassign

Not currently working on upgrades.