This CL enables the framework to manage an arbitrary number of physical
displays. It also surfaces physical display IDs, which are stable across
reboots and encode (model, port) information that will be propagated
further up in a follow-up CL.
Bug: 116025192
Test: Boot with more than two displays
Test: Hotplug works with any number of displays
Test: Verify stable display IDs with "dumpsys display"
Change-Id: Idb2eaff66b2e0873be6ad27d337ff18b730d1331
3316a0a08e