Add last connected device concept

When connecting multiple audio devices
Media and Sonification sounds comes out of the last connected device,
not a high-priority device.

Test: play music
Test: connect wired earphone // sound : wired earphone
Test: connect usb earphone // sound : usb earphone, not the wired earphone(high-priority)
Test: connect bluetooth headset // sound : bluetooth headset
Test: disconnect bluetooth headset // sound : usb earphone, not the wired earphone(high-priority)
Bug: 135749685

Change-Id: I366e136f8e660c4d7f00935cc9088a926c9a605a