Creates implementation for Concurrent displays

Adds the ability to transition to the concurrent
display state, and then present content on that
display. Also provides the ability to add/remove
listeners to know when this feature is available

Extension interface cl: ag/21127264

Bug: 251747141
Test: ExtensionRearDisplayPresentationTest
Change-Id: I1edae8b084d3e3b3f66ce7ced7249812b97c5610
7 files changed