improved target drive selection

[adghayes]

do we have rules defined for which is the right one to choose? perhaps:

• exclude removable drives
• use NVMe if available
• use mmc if NVMe not available
• show options

do we ever have use cases where there are multiple drives we might write to? VxMark?

[adghayes]

Plan talking with @amcmanus:

1. exclude removable drives
2. exclude too-small drives
3. if NVMe, use that
4. else, give the list