allow for more flexibility in the lvcreate API
We currently only allow a 1:1 (device to vg/lv) mapping, but for automatic behavior other flexible combinations will be needed:
- custom percentage
- automatic percentage calculation (e.g. 2 devices out of this NVMe device)
It is still ideal to keep one volume group per device, as that gives a better control at creation time of where an OSD might live.