Return explicit "Other Device" in MediaDeviceManager

Returning an explicit "Other Device" allows us to make sure that the
right icon and name will be set. MediaControlPanel, which consumes the
MediaDeviceData, will otherwise not show a fallback icon if we don't set
one.

Bug: 345799238
Test: atest MediaDeviceManagerTest
Flag: com.android.settingslib.media.flags.use_playback_info_for_routing_controls
Change-Id: I42a1597b5c167a7f41a811c25d87f3134bd73b28