Use RecentTasksListener to trigger TopTaskTracker

Currently launcher gets task stack updates through WM core. Ideally we
would like to migrate into a model where launcher gets these updates
through shell instead.

Test: Manually check that the correct task info is delivered to launcher
from shell
Bug: 341932484
Bug: 344684650
Flag: NONE Just adding a listener, no logic added

Change-Id: Iaf534a4bfee968138d4a4ff282a66e62759af2c0