Did a refactor to better organize the camera flipping code. Also, I
wanted to make sure we handle the cases where the user doesn't have two
cameras (or no cameras, for that matter). In these cases, we just don't
show the appropriate buttons.
If Camera2Enumerator.isSupported() throws, consider Camera2Enumerator to
not be supported, log the Throwable, and use Camera1Enumerator instead.
Before this patch, an exception thrown by Camera2Enumerator.isSupported
would crash any Signal call (even if video was not enabled).
Fixes#6537
// FREEBIE
