Support upgrading minikube VM with contents from a newer ISO

[r2d4]

Is this a BUG REPORT or FEATURE REQUEST? (choose one): feature request

There should be a feature for upgrading the minikube-iso without deleting k8s state.

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

Prevent issues from auto-closing with an /lifecycle frozen comment.

If this issue is safe to close now please do so with /close.

Send feedback to sig-testing, kubernetes/test-infra and/or @fejta.
/lifecycle stale

[r2d4]

/lifecycle frozen

[tstromberg]

NOTE: The implementation of this will be quite tricky and require a design proposal. Here be dragons.