Sled agent fails to adopt disk with 4096 LBA and no GPT labels

Typically disks arrive from the factory with an LBA of 512 and no GPT label set, and adoption sets the LBA to 4096. Recently we needed to remediate some U.2 drives where the LBA remained 512 post-adoption.

After destroying the zpool, we used nvmeadm format nvme4 1, to set the block size to 4096. However, when sled-agent failed to adopt this disk:

00:04:59.662Z WARN SledAgent (ConfigReconcilerTask): Disk adoption failed
    disk_identity = DiskIdentity { vendor: "1b96", model: "SDS6CA264PSP9X3", serial: "372576D0016710" }
    error = Other error starting disk management: Failed to open partition at /devices/pci@3d,0/pci1de,fff8@1,1/pci1b96,2751@0/blkdev@w0014EEB3006A0600,0:wd,raw: No such file or directory (os error 2)
    file = sled-agent/config-reconciler/src/reconciler_task/external_disks.rs:703

Here is the state of the disk per prtvtoc:

22P3T7NX # prtvtoc /devices/pci@3d,0/pci1de,fff8@1,1/pci1b96,2751@0/blkdev@w0014EEB3006A0600,0:c,raw
* /devices/pci@3d,0/pci1de,fff8@1,1/pci1b96,2751@0/blkdev@w0014EEB3006A0600,0:c,raw partition map
*
* Dimensions:
*        4096 bytes/sector
*         112 sectors/track
*         224 tracks/cylinder
*       25088 sectors/cylinder
*       62292 cylinders
*       62292 accessible cylinders
*  1562781696 sectors
*  1562781696 accessible sectors
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                            First       Sector      Last
* Partition  Tag  Flags      Sector       Count      Sector  Mount Directory
       0      0    00            0  1562805846  1562805845
       2      5    01            0  1562805846  1562805845
       8      1    01            0       25088       25087

Some experimentation found only certain combinations of block size and label can be adopted by sled-agent:

Start in sled-agent/config-reconciler/src/reconciler_task/external_disks.rs around line 703, where the missing :wd partition causes adoption to fail. Reproduce or trace the four block-size and GPT-label combinations using prtvtoc and the reported nvmeadm format command. Done means an unlabeled 4096-byte-sector disk can be adopted, while the existing successful cases remain intact.