Fix accessiblity CTS tests (framework).

1. An external contribution changed the ordering of views for
   accessibility. While it attempted to fix a platform issue
   for a comparator breaking transitivity, it changed the way
   we order views and results in very unnatural accessibility
   traversal order. It also broke CTS tets. This change tweaks
   the comparator which fixes the tests and improves traversal
   order.

2. If there is at least one accessibility service which cares
   about windows we register a callback in the window manager
   for window change notifications. We are updating the window
   list on this callback. There was a case where if the service
   requests window updates and immediately asks for the windows
   it gets none as we have not received a callback from the
   window manager yet. Now this call returns after we get the
   callback in a timed fashion. This is consistent with how the
   other introspection APIs work.

3. Window info objects are cached in the accessibility service
   process. When putting them in the cache a cloning call was
   missing resulting in some cases of clobbering windows given
   to the client. For example, we get some windows, cache them,
   and return these windows to the client. Now a call to clear
   the cache arrives while the user processes the windows and
   the client windows get clobbered.

4. Added API for checking if a window has accessiblity focus
   to be consistent to the API we have to check whether this
   window has input focus.

5. Removed some obsolete code.

bug:16402352

Change-Id: Ided6da4a82cc0fc703008c58a2dff0119a3ff317