2/ Add support for dragging shortcuts and tasks

- Add mechanism for creating PendingIntents to launch apps in the same
  way as starting through LauncherApps service
- Require callers starting a task launch to either be the recents
  component or have the START_TASKS_FROM_RECENTS permission

Bug: 169894807
Test: atest LauncherAppsTest
Test: atest DragDropControllerTest
Change-Id: I2f9f622b4ef7a8aba06b0854a1549a2c07cf38e1