Implement AccessibilityDelegateImpl for the Taskbar

- Added accessibility actions to open pop up menu
- Added accessibility actions to open an app/shortcut to the top/left or bottom/right

Fixes: 204453506
Bug: 198438631
Test: attempted all actions individually, attempted combinations of actions (eg. open pop up menu -> move to left/right)
Change-Id: I76a4237035a0ebfe88b8b5f147b574bb2629f20c