Add address to MediaRoute2Info

The route ID of a bluetooth route was its hardware address and
SettingsLib depended on that to get BluetoothDevice.

We can't use the address as ID for a pair of hearing devices,
which has their own address but should have the same route ID.

Instead, this CL adds "address" field explictly to be used for bluetooth
routes.
Maybe it can be used by other devices as well.

Bug: 157708273
Test: make -j42 RunSettingsLibRoboTests && cts test
Change-Id: Ib940da9975fc8d68ec3fb7cf2c4a85c0d1a195f3