low-level: add dump-udev command

low-level: add dump-udev command

Fetches UDEV device properties prepended with 'E:' for NICs and disks.
The result is stored in its own JSON file.

This information is needed to filter for specific devices. Mainly for
the auto-installer for now.

Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
Co-authored-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
 [ TL: rework Udev module to avoid external dependencies, keep those
   in the Sys modules ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>