Add device entry icon support for GONE => LS

The keyguard transition from gone to lockscreen
can happen if the user manually locks down the device.
Add support for this transition to the device entry icon.

Also simplifies `deviceEntryBackgroundViewAlpha` logic.
Each TransitionViewModel doesn't need to check whether
Udfps is supported. Instead, the visibility of the
deviceEntryViewBackground is controlled by the viewBinder
and viewModel.

Test: atest DreamingToLockscreenTransitionViewModelTest AodToLockscreenTransitionViewModelTest
Test: manually enroll UDFPS and then lockdown device from
global actions menu. Observe lock icon on the lockscreen.
Fixes: 323013069
Flag: ACONFIG com.android.systemui.device_entry_udfps_refactor DEVELOPMENT

Change-Id: Id63f9aae68a2f3c35310790b9a5c038aeca624a4