Add AudioProxy HAL IDevicesFactory and IDevice Implementation

The DevicesFactory creates a default DeviceImpl instance, which forwards
openOutputStream() calls to the registered bus device.

The DeviceImpl supports multiple registered bus devices.

Bug: 152919242
Test: Tested on Android TV Device
Change-Id: I61dff6467ed22f293ae227cba39ef5e13eb3925b
10 files changed