Add a minimal FreeformTaskListener

WM team starts to remove functionalities that were made for unmanaged
tasks so take this step 1 to avoid regressions from this type of
changes.

Also remove UNSUPPORTED_WINDOWING_MODES because ShellTaskOrganizer can
handle all windowing modes now.

Bug: 192310211
Bug: 165794880
Bug: 165794636
Test: Maximize, drag and resize freeform windows.
Change-Id: If130b449fe6cf37c39f0e1424e4f23cdb2d33dd5