[Motion] Split-shade expansion: shorten the required drag down amount to fully expand shade

Before, the drag down amount required to fully expand the shade was the entire height of the screen.

Changes:
- Changes the required drag amount distance to a static value in resources. Then uses this value in Npvc#calculatePanelHeightQsExpanded. This then is used to compute the expansion fraction, which is used downstream almost everywhere.
- For the scrim, instead of using the fraction, we introduce another static drag down amount distance value in resources. This is to make sure the timing looks a little better and avoid having a fully black screen when expanding.

Test: Manually
Test: Unit tests
Bug: 214946307
Bug: 229726547
Fixes: 229997327
Change-Id: I3bb21225860b5d49c1b8f15427c9dd85bdbb8c84