Add gradient clock to AOD/LS behind LS flag

Also updates "new lockscreen" smart space layout.

Currently TimeBasedColorsClockController will change the TextClock's
colors based on hardcoded times.
To toggle on the new lockscreen:
  adb shell settings put global show_new_lockscreen 1

Test: atest KeyguardSliceViewTest
Test: manual
Bug: 170228350
Change-Id: Ib72b45aad34fe4483538a9094154d6c473910612