Add "Adaptive sleep" setting

Adaptive sleep setting, if enabled, will perform an attention check
right before the power manager is scheduled to dim and then turn off the
display. If the attention check says that user is currently paying
attention to the device, the screen sleep timeout timer will be reset,
as if user had interacted with the display.

The animation and explanation strings are still TBC per UX team.

The setting is only displayed on supported devices.

Test: make RunSettingsRoboTests
Bug: 111939367
Change-Id: I191dd8ef06ecec4edbe4357671a7a9360971c06f