toollib: handle vg uuid args in process_each_vg

VG uuids can be used in place of VG names as command
args for commands using process_each_vg.  The command
line uuid format includes dashes.

As with tags, processing vg uuid args requires
process_each_vg to read all vgs to match their
uuid against the uuid args.
test: add process-each-vguuid