UX polish for long-press lock screen popup.

The "Lock screen settings" popup that appears when the user long-presses
on the lock screen is receiving the following changes:
1. New icon (palette instead of gears)
2. New text ("Customize lock screen" instead of "Lock screen settings")
3. New coloring - to highlight the button
4. Fixed positioning - right between the two lock screen shortcuts, at
   the bottom
5. New haptic feedback - plays a "tick" vibration when it appears
6. New appear/disappear animations (see recording)
7. Automatic hiding is delayed as long as the finger stays down.
8. A touch ripple is shown when the finger is placed on the popup.
9. With the "direct to WPP" flag turned on, long-pressing directly opens
   wallaper picker.

Flag: LOCK_SCREEN_LONG_PRESS_ENABLED
Bug: 275517886
Test: Added unit tests
Test: Manually verified that all looks good on the following combination
of environments: large screens / hand-held, dark theme / light theme,
gesture nav / nav buttons.

Change-Id: I60d63d6581e5de861c75d20dc8b7ee475239d1cc