cmhw: cmhw: Add UniqueDeviceId support

It's sometimes useful to know what physical device you're using.

CMHW SerialNumber and an "ro.serialno" property already exists, but
are not guaranteed to be unique. Different OEM may use overlapping
numbering schemes, and sometimes placeholder like "012345ABCDE" are
used.

Attempt to work around these shortcomings by defining a new
UniqueDeviceId class that provides a globally unique device ID that
is both deterministic for a given device and designed not to overlap
with IDs of any other devices.

CYNGNOS-2237
Change-Id: I3f426972558394ba8e78261273ac8521aa603327