design-proposal: Introduce LiveUpdate support for instance types

[lyarwood]

What this PR does / why we need it:

The VM Rollout Strategy feature introduced in KubeVirt 1.2 now allows for specific changes made to a running VM to propagate to the VMI without a restart. This design proposal covers extending this support to cover changes made to the referenced instance type or preference of a running VM.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

Special notes for your reviewer:

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR. Approvers are expected to review this list.

• [ ] Design: A design document was considered and is present (link) or not required
• [ ] PR: The PR description is expressive enough and will help future contributors
• [ ] Code: Write code that humans can understand and Keep it simple
• [ ] Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• [ ] Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• [ ] Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• [ ] Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
• [ ] Community: Announcement to kubevirt-dev was considered

Release note:

NONE

[kubevirt-bot]

Skipping CI for Draft Pull Request. If you want CI signal for your change, please convert it to an actual PR. You can still manually trigger a test run with /test all

[lyarwood]

/cc @vladikr

FWIW I took a look at the code and I think this should be pretty straight forward if we apply instance types and preferences before doing the comparisons. Any thoughts?

[lyarwood]

https://github.com/kubevirt/kubevirt/pull/11455 WIP code here that seems to work.

[vladikr]

@lyarwood Thanks! I think it makes a lot of sense to do it now.

[lyarwood]

@vladikr would you mind taking another look at this now it's marked as ready to review?

The PoC code is under https://github.com/kubevirt/kubevirt/pull/11455

[lyarwood]

@vladikr if you have time this week could you take another look at this? The implementation PR is also about to land https://github.com/kubevirt/kubevirt/pull/11455 if you also have time.

[vladikr]

/approve Thanks, very nice! And apologies for the delay.

[kubevirt-bot]

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