Add a staggered delete animation.

For when we long press the delete button for the pin screen, we want to
stagger the deletion of each pin dot. The maximum time for deleting all
of dots does not exceed 200ms.

Fixes: 285828860
Test: long press delete with a bunch of dots
Flag: NONE
Change-Id: Ib7764b77c3adec6508612fe7e2367eee123ca8a2