Initial Taskbar drag-n-drop support for search results.

- Includes initial support for obtaining PendingIntent for ITEM_TYPE_SEARCH_ACTION.
- Custom pre-drag conditions for search results can be provided through TaskbarSearchSessionController.
- Added detection for telling when DragView shift animation ends for
  pre-drag condition usage.

Test: Manual
Bug: 289261756
Flag: ENABLE_ALL_APPS_SEARCH_IN_TASKBAR
Change-Id: I52510a6f3ee49968134ecb591ef7c4df711b9d3d