Add NEW_TASK flag to Quickstep App Widget activity start

Include the NEW_TASK flag to activity starts launched from Quickstep
hosted App Widgets.

This is consistent with the default non-Quickstep generated
ActivityOptions from RemoteViews::getLaunchOptions.

Bug: 169042867
Test: manual
Change-Id: Iba370731f4126d92a11a4e348e74888b533d4d8b