Fix Output Switcher "multiple selected routes"

Issue is caused by PhoneMediaDevice choosing its id according
to the type of the route. As a result, having a USB_DEVICE and
an HDMI device connected simultaneously causes a buggy UI.

See linked bug for details.

Flag: ACONFIG com.android.media.flags.enable_audio_policies_device_and_bluetooth_controller TEAMFOOD
Bug: b/319103067
Test: Manually and with atest SettingsLibRoboTests
Change-Id: Icf928948d8fe80773cc36502b6c8aa0a43f35206