A bunch of public VDM APIs for exposing VD properties.

 - a convinience method for getting a specific device in VDM
 - all displayIds for a specific device
 - whether a device has a custom sensor policy
 - a device listener for create/close events (inspired by
   DisplayManager.DisplayListener and CompanionDeviceManager
   .OnAssociationsChangedListener)

Bug: 276718212
Bug: 297253526
Test: atest VirtualDeviceTest
Change-Id: Iea011eca716b64534de693eb3d92a58ae7f67d9e