Removing supports for creating stack on display

The API of creating a stack on certain display was intended
to create a container that can launch activities within.
Since activities now can be launched to any display by
specifying display id. This is no longer necessary.

Bug: 111363427
Test: atest ActivityManagerPinnedStackTests#testEnterPipWithResumeWhilePausingActivityNoStop

Change-Id: I89635d4e744672b79f5a60a8019f2ff93413e1df