Use RootTaskDisplayAreaOrganizer to obtain TDA windowing mode

CaptionWindowDecorViewModel used to use
WindowConfiguration#getDisplayWindowingMode() to obtain TDA windowing
mode. That flag is to be deprecated and misnamed after we fixed display
windowing mode to fullscreen. This CL removes the dependency on that
field.

Bug: 333724879
Test: Maximize works on CF PC.
Change-Id: Ie29a2b47e626ddf333f762befe12ab6c3618726c