Floss: updating enum BtDeviceType and changing its default value

Aligning the definition with enum BluetoothDeviceType in Chromium.
In case topshim gets an invalid device type from libbluetooth,
it will be converted to 'Unknown' device type for correctness and
clarity.

Bug: 231248387
Tag: #floss
Test: manual test on classic and dual mode devices
Change-Id: Ieac91b26f13958ce974f528ac476f85594beb08b