Override the fillsParent() on TaskFragment

The default implementation of fillsParent() on TaskFragment which
results in the system can not get the specified orientation from the
activity in TaskFragment when traversing the windowContainers with
getOrientation().

Move the implementation of fillsParent() from Task to TaskFragment.
Report the taskFragment fills the parent in a full screen window
or matches the parents' bounds. So, we can get the orientation from
activity successfully.

Bug: 207605841
Test: Launch wallpaper picker and check the orientation when rotate
Change-Id: Ieb7e7e009fcfb337b2c7def1b892831d09d98951