Update rotation suggestion button position to align it with taskbar

This CL moves the rotation suggestion button to the middle
of the taskbar when it is visible and not stashed.
When the user stashes or unstashes the taskbar the
button's position is animated accordingly.

Test: manual
Test: atest com.android.systemui.navigationbar.gestural.FloatingRotationButtonPositionCalculatorTest
Fixes: 187410455
Change-Id: Id918e10a44631362f7c3a8a8bb624ee80bdd3c8b