format(1M) and prtvtoc(1M) need to handle all EFI GUIDs
format(1M) and prtvtoc(1M) were designed to work with traditional VTOC labels only and currently only understand EFI GUIDs that have been mapped to some VTOC equivalent. libefi skips GPT partitions with unrecognised GUIDs because the tools can't deal with them. For this reason the assert in #934 happens for an unrecognised GUID. The tools need to be modernised.