Use String for display name in VirtualCameraConfig

... instead of resource id.

It's trivial to get fetch the string for the resource id
for the client, but not possible to do the opposite.

This is also consistent will all other Virtual*Config which
use Strings for display names.

Bug: 310857519
Test: atest CtsVirtualDevicesCameraTestCases
Change-Id: I98080fd3a4142c910ebb5daf102e7eee2181f51e