Make media squishy for portrait shade open and close

Propagate squishFraction from QSFragment to MediaHostState.

In MediaViewController, apply squishFraction to both
cached and uncached UMO viewStates.

Remove mTopPadding (qsHeight / space above lockscreen notifs)
from expansionFraction (aka squishFraction) calculations to avoid
the following recursion:
=> squishFraction changes UMO height
=> new UMO height changes mTopPadding
=> mTopPadding changes total stack height
=> new stack height changes squishFraction

Use expandedFraction calculated in PVC instead of recalculating it
in NSSL.

Bug: 217583474
Test: MediaViewControllerTest
Test: open/close portrait shade => squishy UMO

Change-Id: Ifdada015563394a96c3d80ae527c68ac7323d4c2