SQL Schema have a virtual table to check for invalid descriptors in a cluster. Restore and import are in the business of creating and ingesting descriptors, and so we should check the virtual table post restore/import for any invalid descriptor states they might have generated. This should be added to as many restore/import tests as possible, but also potentially as a sanity check during a restore/import once the descriptors have been published to an online state.

Jira issue: CRDB-17847