Plan Wizard: Select VMs step: add case for "unknown" analytics status (use revisionAnalyzed property)

[mturley]

Related to #126, could be the same PR (finalizing all the stuff about that migration analytics column).

Slack message from Jeff:

I posted on Sat that my PSI cluster has initial MA integration w/ provider inventory and the concerns are now based on MA. You'll notice a few other things. 1. All resources now have a revision field that is incremented on update. 2. The VM has a revisionAnalyzed field that indicates which revision the concerns are based on. If the revisionAnalyzed < revision, the UI should interpret as unknwon and recommend something like a ❓ icon. (edited)
Changes are analyzed asynchronously so could be a short window where the VM update is reflected in the inventory and the analytics has not been updated.

We need to make sure to handle that revisionAnalyzed < revision case and display an "unknown" message. We could perhaps add an "unknown" variant to the StatusIcon in lib-ui.

[mturley]

Related: #126

[mturley]

Note: we should make sure we have polling enabled for this data so the unknown case will go away if it is updated in the API. I think we may have turned off polling for the wizard.