Used different curve for the icons when expanding

The icon animation has now a different interpolator when
expanding compared to when fully expanded. this makes sure
that its moving nicely linear when fully expanded, but in
an accelerate decelerated manner when not.

Test: Add notifications, observe interpolators
Bug: 32437839
Change-Id: I3efcaf54e012f8462bc21ff819903c22d8a1af21