[CD Taskbar] Refactor TaskbarManager - Make mAddedWindow display-specifc

Create SparseBooleanArray to ensure that with connected displays, there is support for multiple RootLayouts, which each a variable tracking whether they have been added to the window or not.

Flag: EXEMPT not adding new behavior
Bug: 384793943
Test: Manual
Change-Id: I18849d033cada181eadf89c86d3c02d87a8ee962