Migrate from using taskIDs to taskViewIDs in RecentsView

* Follow up CL coming to introduce a TaskView that
can have multiple Tasks, so a taskID won't be particularly useful
in that scenario.

Bug: 192292305
Test: Manual, w/ and w/o live tile
Change-Id: I1900b999ac51aa99923239f2af400c90c71c3dae
6 files changed