In 22.2 we published https://www.cockroachlabs.com/docs/v22.2/restoring-backups-across-versions.html which outlines our policy for restoring older backups. We should enforce this policy in code so that we are able to provide stronger guarantees about what we test and support. Furthermore, this will allow us to cleanup legacy code that was kept around to support restoring backups outside our supported window.

Jira issue: CRDB-22806
Epic CRDB-22861