Supporting more programmatic progress changes in haptics sliders.

The default SliderStateTracker can also handle cases in which progress
changes occur in a slider when the tracker is IDLE. This can happen if
the slider reached a bookend (and resets to IDLE) but the program
continues to supply progress changes. Before, slider haptics would
remain stuck in the IDLE state until the state logic was reset by
terminating the slider interaction.

Test: added Unit tests to SliderStateTrackerTest
Test: manual. Verified haptics continue to work on the volume slider by
 using the volume keys after reaching either bookend.
Bug: 406120925
Flag: EXEMPT bug fix
Change-Id: I3eed6dd37e4e502c280c0a696732a04ca28dfddf