feat(scripts): add lvm-thin-helper script

[Kuruyia]

Must be merged after #19.

[Kuruyia]

Opening this as draft for now since this is clearly not finished.

Currently, the scripts returns all PVs that are actively used by, and all LVs that have segments provisioned in a thin pool LV. I don't know if that's enough or if we want more info, or something else entirely.

$ lvm-thin-helper linstor_group thin_device
XCP-storage: [73717] - core - INFO - Running command `lvm fullreport --reportformat json linstor_group`.
{"pvs": ["/dev/disk/by-id/nvme-QEMU_NVMe_Ctrl_nvme0_3", "/dev/disk/by-id/nvme-QEMU_NVMe_Ctrl_nvme0_2"], "lvs": ["xcp-persistent-database_00000", "xcp-volume-4ad561ce-0cfd-4f9c-9e39-bb464e095b05_00000"]}

cc @Wescoeur